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Thinka Nov 2023 (V2) Cambridge International A Level-Style Mock — Mathematics (0580)

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An original Thinka practice paper modelled on the structure and difficulty of the Nov 2023 (V2) Cambridge International A Level Mathematics (0580) paper. Not affiliated with or reproduced from Cambridge.

Paper 22 Extended

Answer all questions. Use a calculator where appropriate. Show all necessary working clearly.
26 PastPaper.question · 70.20000000000003 PastPaper.marks
PastPaper.question 1 · short_answer
2.7 PastPaper.marks
Simplify fully \(\frac{2x^2 - 5x - 3}{4x^2 - 1}\).
PastPaper.showAnswers

PastPaper.workedSolution

Factorise the numerator: \(2x^2 - 5x - 3 = (2x + 1)(x - 3)\). Factorise the denominator: \(4x^2 - 1 = (2x - 1)(2x + 1)\). Divide both by the common factor \(2x + 1\) to obtain the simplified fraction: \(\frac{x - 3}{2x - 1}\).

PastPaper.markingScheme

M1 for factorising numerator: \((2x + 1)(x - 3)\); M1 for factorising denominator: \((2x - 1)(2x + 1)\); A1 for final answer \(\frac{x - 3}{2x - 1}\)
PastPaper.question 2 · short_answer
2.7 PastPaper.marks
In a clearance sale, the price of a laptop is reduced by 15% to \(\$459\). Calculate the original price of the laptop.
PastPaper.showAnswers

PastPaper.workedSolution

Let the original price be \(x\). A 15% reduction means the sale price is 85% of the original price. Therefore, \(0.85x = 459\), which gives \(x = \frac{459}{0.85} = 540\).

PastPaper.markingScheme

M1 for setting up \(0.85x = 459\) or \(\frac{459}{85} \times 100\); A1 for 540
PastPaper.question 3 · short_answer
2.7 PastPaper.marks
A solid cone has a base radius of \(6\text{ cm}\) and a slant height of \(10\text{ cm}\). Calculate the total surface area of the cone, leaving your answer in terms of \(\pi\).
PastPaper.showAnswers

PastPaper.workedSolution

The formula for the total surface area of a cone is \(A = \pi r^2 + \pi r l\), where \(r\) is the radius and \(l\) is the slant height. Substituting the given values: \(A = \pi(6)^2 + \pi(6)(10) = 36\pi + 60\pi = 96\pi\text{ cm}^2\).

PastPaper.markingScheme

M1 for correctly substituting into \(\pi r^2 + \pi r l\): \(\pi (6)^2 + \pi (6)(10)\); A1 for \(96\pi\)
PastPaper.question 4 · short_answer
2.7 PastPaper.marks
In triangle \(ABC\), \(AB = 7\text{ cm}\), \(BC = 8\text{ cm}\), and \(AC = 9\text{ cm}\). Calculate angle \(BAC\). Give your answer correct to 1 decimal place.
PastPaper.showAnswers

PastPaper.workedSolution

Using the cosine rule: \(BC^2 = AB^2 + AC^2 - 2 \cdot AB \cdot AC \cdot \cos(BAC)\). Substituting the lengths: \(8^2 = 7^2 + 9^2 - 2(7)(9)\cos(A)\) which simplifies to \(64 = 49 + 81 - 126\cos(A)\). Then \(126\cos(A) = 130 - 64 = 66\), so \(\cos(A) = \frac{66}{126}\). Thus, \(A = \arccos\left(\frac{11}{21}\right) \approx 58.41^{\circ}\).

PastPaper.markingScheme

M1 for applying the cosine rule correctly: \(8^2 = 7^2 + 9^2 - 2(7)(9)\cos(A)\); M1 for rearranging to find \(\cos(A) = \frac{66}{126}\); A1 for \(58.4\) (or \(58.4^{\circ}\))
PastPaper.question 5 · short_answer
2.7 PastPaper.marks
A bag contains 5 red marbles and 3 blue marbles. Two marbles are selected at random from the bag without replacement. Calculate the probability that both marbles are of the same color.
PastPaper.showAnswers

PastPaper.workedSolution

The probability of selecting two red marbles is \(P(\text{R, R}) = \frac{5}{8} \times \frac{4}{7} = \frac{20}{56}\). The probability of selecting two blue marbles is \(P(\text{B, B}) = \frac{3}{8} \times \frac{2}{7} = \frac{6}{56}\). The probability of selecting two marbles of the same color is \(P(\text{R, R}) + P(\text{B, B}) = \frac{20}{56} + \frac{6}{56} = \frac{26}{56} = \frac{13}{28}\).

PastPaper.markingScheme

M1 for finding \(P(\text{R, R}) = \frac{20}{56}\) or \(P(\text{B, B}) = \frac{6}{56}\); M1 for adding the two probabilities: \(\frac{20}{56} + \frac{6}{56}\); A1 for \(\frac{13}{28}\) (or 3sf decimal equivalent \(0.464\))
PastPaper.question 6 · short_answer
2.7 PastPaper.marks
A ladder of length \(5\text{ m}\) leans against a vertical wall. The foot of the ladder is \(1.5\text{ m}\) from the base of the wall. The ladder slips down so that its top is now \(0.8\text{ m}\) lower down the wall. Calculate the new distance of the foot of the ladder from the base of the wall. Give your answer correct to 2 decimal places.
PastPaper.showAnswers

PastPaper.workedSolution

Using Pythagoras' theorem, the initial height of the top of the ladder is \(h_1 = \sqrt{5^2 - 1.5^2} = \sqrt{22.75} \approx 4.7697\text{ m}\). After slipping down by \(0.8\text{ m}\), the new height is \(h_2 = 4.7697 - 0.8 = 3.9697\text{ m}\). The new distance of the foot of the ladder from the wall is \(d = \sqrt{5^2 - h_2^2} = \sqrt{25 - (3.9697)^2} = \sqrt{25 - 15.7585} = \sqrt{9.2415} \approx 3.04\text{ m}\).

PastPaper.markingScheme

M1 for finding the initial height: \(\sqrt{5^2 - 1.5^2} \approx 4.77\); M1 for finding the new distance using Pythagoras with the new height: \(\sqrt{5^2 - (4.77 - 0.8)^2}\); A1 for \(3.04\)
PastPaper.question 7 · short_answer
2.7 PastPaper.marks
The table shows information about the times, \(t\) minutes, taken by 40 students to complete a puzzle: \(0 < t \le 10\) has frequency 8, \(10 < t \le 20\) has frequency 15, \(20 < t \le 30\) has frequency 11, and \(30 < t \le 40\) has frequency 6. Calculate an estimate of the mean time taken.
PastPaper.showAnswers

PastPaper.workedSolution

First, find the midpoints of each interval: \(5, 15, 25, 35\). Next, calculate the sum of the products of each midpoint and its corresponding frequency: \(8 \times 5 + 15 \times 15 + 11 \times 25 + 6 \times 35 = 40 + 225 + 275 + 210 = 750\). Divide by the total frequency (40): \(\text{Mean} = \frac{750}{40} = 18.75\text{ minutes}\).

PastPaper.markingScheme

M1 for calculating at least three correct midpoints \(5, 15, 25, 35\); M1 for calculating \(\sum f \cdot x = 750\); A1 for \(18.75\)
PastPaper.question 8 · short_answer
2.7 PastPaper.marks
Triangle \(A\) has vertices at \((1, 1)\), \((3, 1)\), and \((1, 4)\). Triangle \(B\) has vertices at \((-2, -2)\), \((-6, -2)\), and \((-2, -8)\). Describe fully the single transformation that maps triangle \(A\) onto triangle \(B\).
PastPaper.showAnswers

PastPaper.workedSolution

Comparing corresponding sides, the width of triangle \(A\) is \(3 - 1 = 2\) units, and the width of triangle \(B\) is \(-6 - (-2) = -4\) units. The ratio is \(\frac{-4}{2} = -2\), indicating a scale factor of \(-2\). The lines connecting corresponding vertices \((1,1)\) to \((-2,-2)\), \((3,1)\) to \((-6,-2)\), and \((1,4)\) to \((-2,-8)\) all intersect at the origin \((0,0)\). Therefore, the transformation is an enlargement with scale factor \(-2\) and center of enlargement \((0,0)\).

PastPaper.markingScheme

B1 for 'Enlargement'; B1 for scale factor \(-2\); B1 for center of enlargement \((0,0)\) or origin
PastPaper.question 9 · short_answer
2.7 PastPaper.marks
Simplify completely: \(\frac{3x^2 - 14x - 5}{x^2 - 25}\)
PastPaper.showAnswers

PastPaper.workedSolution

First, factorise the numerator and the denominator:

Numerator: \(3x^2 - 14x - 5 = (3x + 1)(x - 5)\)
Denominator: \(x^2 - 25 = (x - 5)(x + 5)\)

Now rewrite the fraction:
\(\frac{(3x + 1)(x - 5)}{(x - 5)(x + 5)}\)

Cancel the common factor of \((x - 5)\):
\(\frac{3x + 1}{x + 5}\)

PastPaper.markingScheme

M1 for factorising the numerator to \((3x + 1)(x - 5)\)
M1 for factorising the denominator to \((x - 5)(x + 5)\)
A1 for final correct simplified fraction \(\frac{3x + 1}{x + 5}\)
PastPaper.question 10 · short_answer
2.7 PastPaper.marks
A solid metal sphere of radius \(4\text{ cm}\) is melted down and recast into a solid right circular cone of base radius \(3\text{ cm}\). Calculate the height of the cone. Give your answer correct to 3 significant figures.
PastPaper.showAnswers

PastPaper.workedSolution

The volume of a sphere is given by \(V_{\text{sphere}} = \frac{4}{3}\pi r^3\).
\(V_{\text{sphere}} = \frac{4}{3} \times \pi \times 4^3 = \frac{256}{3}\pi\text{ cm}^3\).

The volume of a cone is given by \(V_{\text{cone}} = \frac{1}{3}\pi R^2 h\).
\(V_{\text{cone}} = \frac{1}{3} \times \pi \times 3^2 \times h = 3\pi h\).

Since the volume remains the same:
\(3\pi h = \frac{256}{3}\pi\)
\(3h = \frac{256}{3}\)
\(h = \frac{256}{9} \approx 28.4\text{ cm}\).

PastPaper.markingScheme

M1 for correct volume of the sphere expression: \(\frac{256}{3}\pi\)
M1 for equating their sphere volume to the cone volume formula and attempting to solve for \(h\)
A1 for \(28.4\) (or \(256/9\))
PastPaper.question 11 · short_answer
2.7 PastPaper.marks
A ladder of length \(6.5\text{ m}\) leans against a vertical wall. The base of the ladder is \(2.5\text{ m}\) from the bottom of the wall on horizontal ground. Calculate the angle the ladder makes with the horizontal ground. Give your answer correct to 1 decimal place.
PastPaper.showAnswers

PastPaper.workedSolution

Let \(\theta\) be the angle the ladder makes with the horizontal ground. The ladder represents the hypotenuse of a right-angled triangle, and the distance from the wall is the adjacent side.

Using the cosine ratio:
\(\cos(\theta) = \frac{\text{Adjacent}}{\text{Hypotenuse}} = \frac{2.5}{6.5} = \frac{5}{13}\)

\(\theta = \cos^{-1}\left(\frac{5}{13}\right) \approx 67.38^\circ\)

To 1 decimal place, \(\theta = 67.4^\circ\).

PastPaper.markingScheme

M1 for setting up the correct trigonometric equation, e.g., \(\cos(\theta) = \frac{2.5}{6.5}\)
A1 for \(67.4\)
PastPaper.question 12 · short_answer
2.7 PastPaper.marks
The table shows information about the masses, \(m\) grams, of 50 apples.

\(\begin{array}{|c|c|} \hline \text{Mass } (m \text{ g}) & \text{Frequency} \\ \hline 80 < m \le 100 & 12 \\ 100 < m \le 120 & 18 \\ 120 < m \le 140 & 15 \\ 140 < m \le 160 & 5 \\ \hline \end{array}\)

Calculate an estimate of the mean mass of these apples.
PastPaper.showAnswers

PastPaper.workedSolution

Find the midpoint of each interval:
- \(80 < m \le 100\): midpoint = \(90\)
- \(100 < m \le 120\): midpoint = \(110\)
- \(120 < m \le 140\): midpoint = \(130\)
- \(140 < m \le 160\): midpoint = \(150\)

Calculate the sum of \(\text{frequency} \times \text{midpoint}\):
\(\sum f x = (12 \times 90) + (18 \times 110) + (15 \times 130) + (5 \times 150)\)
\(\sum f x = 1080 + 1980 + 1950 + 750 = 5760\)

Divide the sum by the total frequency:
\(\text{Estimate of mean} = \frac{5760}{50} = 115.2\text{ g}\).

PastPaper.markingScheme

M1 for finding the correct midpoints (90, 110, 130, 150)
M1 for finding \(\sum f x = 5760\)
A1 for \(115.2\)
PastPaper.question 13 · short_answer
2.7 PastPaper.marks
After a 15% discount, the price of a bicycle is \(\$357\). Calculate the original price of the bicycle before the discount.
PastPaper.showAnswers

PastPaper.workedSolution

The discounted price represents \(100\% - 15\% = 85\%\) of the original price.

Let \(P\) be the original price:
\(0.85 \times P = 357\)

\(P = \frac{357}{0.85} = 420\)

Therefore, the original price was \(\$420\).

PastPaper.markingScheme

M1 for setting up the equation \(0.85 \times P = 357\) or equivalent division \(\frac{357}{0.85}\)
A1 for \(420\)
PastPaper.question 14 · short_answer
2.7 PastPaper.marks
In triangle \(ABC\), \(AB = 8.4\text{ cm}\), \(AC = 6.5\text{ cm}\) and angle \(BAC = 42^\circ\). Calculate the length of \(BC\). Give your answer correct to 3 significant figures.
PastPaper.showAnswers

PastPaper.workedSolution

Using the cosine rule:
\(BC^2 = AB^2 + AC^2 - 2 \times AB \times AC \times \cos(BAC)\)
\(BC^2 = 8.4^2 + 6.5^2 - 2 \times 8.4 \times 6.5 \times \cos(42^\circ)\)
\(BC^2 = 70.56 + 42.25 - 109.2 \times \cos(42^\circ)\)
\(BC^2 \approx 112.81 - 109.2 \times 0.74314...\)
\(BC^2 \approx 112.81 - 81.1514...\)
\(BC^2 \approx 31.658...\)
\(BC = \sqrt{31.658...} \approx 5.6265...\text{ cm}\)

To 3 significant figures, \(BC = 5.63\text{ cm}\).

PastPaper.markingScheme

M1 for substituting correctly into the cosine rule: \(8.4^2 + 6.5^2 - 2 \times 8.4 \times 6.5 \times \cos(42^\circ)\)
A1 for intermediate value \(BC^2 \approx 31.66\) or \(BC = \sqrt{31.66}\)
A1 for \(5.63\) (allow answers in the range \(5.62\) to \(5.63\))
PastPaper.question 15 · short_answer
2.7 PastPaper.marks
Triangle \(A\) has vertices at \((1, 1)\), \((3, 1)\), and \((3, 4)\). Triangle \(B\) has vertices at \((-1, -1)\), \((-1, -3)\), and \((-4, -3)\). Describe fully the single transformation that maps triangle \(A\) onto triangle \(B\).
PastPaper.showAnswers

PastPaper.workedSolution

Let us check the coordinates of mapped vertices:
- \((1, 1) \to (-1, -1)\)
- \((3, 1) \to (-1, -3)\)
- \((3, 4) \to (-4, -3)\)

We see that for each point \((x, y)\), the image point is \((-y, -x)\).
This is the coordinate mapping rule for a reflection in the line \(y = -x\).

PastPaper.markingScheme

M1 for identifying the transformation as a 'Reflection'
A1 for identifying the line of reflection as \(y = -x\)
PastPaper.question 16 · short_answer
2.7 PastPaper.marks
A bag contains 5 red beads and 3 blue beads. Two beads are selected at random without replacement. Calculate the probability that both beads selected are the same colour. Give your answer as a fraction in its simplest form.
PastPaper.showAnswers

PastPaper.workedSolution

The total number of beads is \(5 + 3 = 8\).

Probability of selecting two red beads:
\(P(\text{Red, Red}) = \frac{5}{8} \times \frac{4}{7} = \frac{20}{56}\)

Probability of selecting two blue beads:
\(P(\text{Blue, Blue}) = \frac{3}{8} \times \frac{2}{7} = \frac{6}{56}\)

Probability that both beads are the same colour:
\(P(\text{Same Colour}) = P(\text{Red, Red}) + P(\text{Blue, Blue}) = \frac{20}{56} + \frac{6}{56} = \frac{26}{56} = \frac{13}{28}\).

PastPaper.markingScheme

M1 for \(\frac{5}{8} \times \frac{4}{7}\) or \(\frac{3}{8} \times \frac{2}{7}\)
M1 for addition of their two calculated probabilities
A1 for \(13/28\)
PastPaper.question 17 · short_answer
2.7 PastPaper.marks
Simplify fully: \(\frac{2x^2 - 5x - 3}{4x^2 - 1}\)
PastPaper.showAnswers

PastPaper.workedSolution

First, factorise the numerator by splitting the middle term or by inspection: \(2x^2 - 5x - 3 = 2x^2 - 6x + x - 3 = 2x(x - 3) + 1(x - 3) = (2x + 1)(x - 3)\). Next, factorise the denominator as a difference of two squares: \(4x^2 - 1 = (2x)^2 - 1^2 = (2x + 1)(2x - 1)\). Now, divide the numerator and the denominator by their common factor, \(2x + 1\): \(\frac{(2x+1)(x-3)}{(2x+1)(2x-1)} = \frac{x-3}{2x-1}\).

PastPaper.markingScheme

M1 for factorising the numerator correctly: \((2x + 1)(x - 3)\)
M1 for factorising the denominator correctly: \((2x + 1)(2x - 1)\)
A0.7 for the final simplified fraction \(\frac{x-3}{2x-1}\)
PastPaper.question 18 · short_answer
2.7 PastPaper.marks
A solid cylinder has radius \(r\) and height \(2r\). A solid sphere has radius \(r\). Find the ratio of the volume of the sphere to the volume of the cylinder. Give your answer in its simplest form.
PastPaper.showAnswers

PastPaper.workedSolution

The volume of a sphere of radius \(r\) is given by the formula \(V_{\text{sphere}} = \frac{4}{3}\pi r^3\). The volume of a cylinder of radius \(r\) and height \(h = 2r\) is given by \(V_{\text{cylinder}} = \pi r^2 h = \pi r^2 (2r) = 2\pi r^3\). To find the ratio of the volume of the sphere to the volume of the cylinder, we write: \(\frac{4}{3}\pi r^3 : 2\pi r^3\). Dividing both parts of the ratio by \(\pi r^3\) gives: \(\frac{4}{3} : 2\). Multiplying both parts by 3 to clear the fraction gives: \(4 : 6\). Simplifying this ratio to its lowest terms gives: \(2 : 3\).

PastPaper.markingScheme

M1 for expressing cylinder volume as \(2\pi r^3\) or sphere volume as \(\frac{4}{3}\pi r^3\)
M1 for setting up ratio \(\frac{4}{3}\pi r^3 : 2\pi r^3\) and attempting to simplify
A0.7 for \(2:3\)
PastPaper.question 19 · short_answer
2.7 PastPaper.marks
In triangle \(ABC\), \(AB = 7\text{ cm}\), \(BC = 8\text{ cm}\), and \(AC = 13\text{ cm}\). Calculate the size of angle \(ABC\).
PastPaper.showAnswers

PastPaper.workedSolution

Using the Cosine Rule to find the angle \(ABC\) (which we can call angle \(B\)), we have: \(b^2 = a^2 + c^2 - 2ac \cos(B)\). Here, \(b = AC = 13\), \(a = BC = 8\), and \(c = AB = 7\). Substituting these values into the formula: \(13^2 = 8^2 + 7^2 - 2(8)(7) \cos(B)\) which simplifies to \(169 = 64 + 49 - 112 \cos(B)\). Simplify further: \(169 = 113 - 112 \cos(B)\). Rearranging to solve for \(\cos(B)\): \(112 \cos(B) = 113 - 169\), which gives \(112 \cos(B) = -56\). Thus, \(\cos(B) = -\frac{56}{112} = -0.5\). Calculating the inverse cosine: \(B = \arccos(-0.5) = 120^\circ\).

PastPaper.markingScheme

M1 for substituting correctly into the Cosine Rule: \(13^2 = 8^2 + 7^2 - 2(8)(7)\cos(B)\)
M1 for reaching \(\cos(B) = -0.5\)
A0.7 for \(120\)
PastPaper.question 20 · short_answer
2.7 PastPaper.marks
A bag contains 5 red beads and 3 blue beads. Two beads are selected at random from the bag, one after the other, without replacement. Calculate the probability that the two beads selected have different colours.
PastPaper.showAnswers

PastPaper.workedSolution

The total number of beads initially is \(5 + 3 = 8\). We want to find the probability of selecting beads of different colours, which can happen in two ways: (Red, Blue) or (Blue, Red). First, the probability of selecting a Red bead then a Blue bead: \(P(\text{Red, Blue}) = \frac{5}{8} \times \frac{3}{7} = \frac{15}{56}\). Second, the probability of selecting a Blue bead then a Red bead: \(P(\text{Blue, Red}) = \frac{3}{8} \times \frac{5}{7} = \frac{15}{56}\). Since these two outcomes are mutually exclusive, we add their probabilities to find the total probability: \(P(\text{different colours}) = \frac{15}{56} + \frac{15}{56} = \frac{30}{56} = \frac{15}{28}\) (or approximately \(0.536\)).

PastPaper.markingScheme

M1 for calculating the probability of one combination, e.g., \(\frac{5}{8} \times \frac{3}{7} = \frac{15}{56}\)
M1 for adding the two correct combinations: \(\frac{15}{56} + \frac{15}{56}\)
A0.7 for \(\frac{15}{28}\) (or equivalent fraction/decimal)
PastPaper.question 21 · short_answer
2.7 PastPaper.marks
After a 15% price reduction in a sale, the cost of a laptop is \(\$578\). Calculate the original price of the laptop.
PastPaper.showAnswers

PastPaper.workedSolution

The reduced price of \(\$578\) represents \(100\% - 15\% = 85\%\) of the original price. Let \(x\) represent the original price. We can write the equation: \(0.85x = 578\). To find \(x\), divide both sides by \(0.85\): \(x = \frac{578}{0.85} = 680\). Thus, the original price of the laptop was \(\$680\).

PastPaper.markingScheme

M1 for equating \(85\%\) to \(\$578\) or writing \(578 \div 0.85\)
A1.7 for \(680\)
PastPaper.question 22 · short_answer
2.7 PastPaper.marks
The point \(P(3, -2)\) is reflected in the line \(y = x\) to give point \(Q\). Point \(Q\) is then translated by the vector \(\begin{pmatrix} -4 \\ 5 \end{pmatrix}\) to give point \(R\). Find the coordinates of \(R\).
PastPaper.showAnswers

PastPaper.workedSolution

When a point \((x, y)\) is reflected in the line \(y = x\), its coordinates swap places to become \((y, x)\). Reflecting \(P(3, -2)\) gives \(Q(-2, 3)\). Next, we translate \(Q(-2, 3)\) by the vector \(\begin{pmatrix} -4 \\ 5 \end{pmatrix}\). The new coordinates are: \(x = -2 + (-4) = -6\) and \(y = 3 + 5 = 8\). Therefore, the coordinates of \(R\) are \((-6, 8)\).

PastPaper.markingScheme

M1 for finding the correct coordinates of \(Q = (-2, 3)\)
M1 for adding the translation vector components to their \(Q\) coordinates
A0.7 for \((-6, 8)\)
PastPaper.question 23 · short_answer
2.7 PastPaper.marks
A set of 5 numbers has a mean of 12. When a 6th number is added to the set, the mean of the 6 numbers becomes 13.5. Find the value of the 6th number.
PastPaper.showAnswers

PastPaper.workedSolution

The sum of the initial set of 5 numbers is \(5 \times 12 = 60\). The sum of the new set of 6 numbers is \(6 \times 13.5 = 81\). The value of the 6th number is the difference between these two sums: \(81 - 60 = 21\).

PastPaper.markingScheme

M1 for calculating the sum of either the first 5 numbers (\(60\)) or all 6 numbers (\(81\))
M1 for subtracting the sum of 5 numbers from the sum of 6 numbers: \(81 - 60\)
A0.7 for \(21\)
PastPaper.question 24 · short_answer
2.7 PastPaper.marks
A ladder of length 6.5 metres leans against a vertical wall. The foot of the ladder is 2.5 metres from the base of the wall. Calculate the height up the wall that the ladder reaches.
PastPaper.showAnswers

PastPaper.workedSolution

The ladder, the ground, and the wall form a right-angled triangle. Let \(h\) be the height up the wall reached by the ladder. By Pythagoras' theorem, we have: \(h^2 + 2.5^2 = 6.5^2\). Substituting the squared terms: \(h^2 + 6.25 = 42.25\). Rearranging gives \(h^2 = 42.25 - 6.25 = 36\). Taking the square root: \(h = \sqrt{36} = 6\) metres.

PastPaper.markingScheme

M1 for setting up Pythagoras' theorem: \(h^2 + 2.5^2 = 6.5^2\) or \(h = \sqrt{6.5^2 - 2.5^2}\)
M1 for evaluating \(h^2 = 36\)
A0.7 for \(6\)
PastPaper.question 25 · short_answer
2.7 PastPaper.marks
Simplify completely \(\frac{2x^2 - 8}{x^2 - x - 6}\).
PastPaper.showAnswers

PastPaper.workedSolution

First, factorise the numerator by factoring out the common term and then using the difference of two squares:
\(2x^2 - 8 = 2(x^2 - 4) = 2(x - 2)(x + 2)\)

Next, factorise the quadratic expression in the denominator:
\(x^2 - x - 6 = (x - 3)(x + 2)\)

Substitute the factorised terms back into the fraction:
\(\frac{2(x - 2)(x + 2)}{(x - 3)(x + 2)}\)

Cancel the common factor of \(x + 2\) from the numerator and the denominator:
\(\frac{2(x - 2)}{x - 3}\) or \(\frac{2x - 4}{x - 3}\)

PastPaper.markingScheme

M1 for factorising the numerator to \(2(x-2)(x+2)\)
M1 for factorising the denominator to \((x-3)(x+2)\)
A0.7 for the final answer \(\frac{2(x-2)}{x-3}\) or \(\frac{2x-4}{x-3}\)
PastPaper.question 26 · short_answer
2.7 PastPaper.marks
An antique clock increases in value by 15% in its first year. In the second year, its value increases by a further 8% of its new value. At the end of the second year, the clock is worth $1863. Calculate the value of the clock at the start of the first year.
PastPaper.showAnswers

PastPaper.workedSolution

Let \(V\) be the initial value of the clock.

After a 15% increase in the first year, the value becomes:
\(V \times 1.15\)

After an 8% increase in the second year, the value becomes:
\(V \times 1.15 \times 1.08 = V \times 1.242\)

We are given that the final value is $1863:
\(1.242V = 1863\)

Solve for \(V\):
\(V = \frac{1863}{1.242} = 1500\)

The initial value of the clock was $1500.

PastPaper.markingScheme

M1 for a correct product of multipliers, e.g., \(1.15 \times 1.08\) or \(1.242\)
M1 for setting up the equation \(V \times 1.242 = 1863\) or for finding the intermediate value \(\frac{1863}{1.08} = 1725\)
A0.7 for the final answer of 1500

Paper 42 Extended

Answer all questions. Show all necessary working clearly. Answers to non-exact values should be given to 3 significant figures.
11 PastPaper.question · 130.39999999999998 PastPaper.marks
PastPaper.question 1 · structured_multipart
11.8 PastPaper.marks
This question is about algebraic manipulation.

(a) Simplify completely:
$$\frac{2x^2 - 5x - 3}{4x^2 - 1}$$

(b) Solve the equation:
$$\frac{3}{y+2} + \frac{5}{2y-1} = 2$$
Show all your working and give your answers correct to 2 decimal places.

(c) Express as a single fraction in its simplest form:
$$\frac{4}{x-3} - \frac{3}{x+1}$$
PastPaper.showAnswers

PastPaper.workedSolution

**(a)**
Factorise the numerator:
$$2x^2 - 5x - 3 = (2x + 1)(x - 3)$$
Factorise the denominator as a difference of two squares:
$$4x^2 - 1 = (2x + 1)(2x - 1)$$
Simplify by cancelling the common factor $(2x + 1)$:
$$\frac{(2x + 1)(x - 3)}{(2x + 1)(2x - 1)} = \frac{x - 3}{2x - 1}$$

**(b)**
Multiply each term by the common denominator $(y+2)(2y-1)$:
$$3(2y - 1) + 5(y + 2) = 2(y + 2)(2y - 1)$$
$$6y - 3 + 5y + 10 = 2(2y^2 + 3y - 2)$$
$$11y + 7 = 4y^2 + 6y - 4$$
Rearrange to form a quadratic equation equal to zero:
$$4y^2 - 5y - 11 = 0$$
Apply the quadratic formula $y = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$:
$$y = \frac{-(-5) \pm \sqrt{(-5)^2 - 4(4)(-11)}}{2(4)}$$
$$y = \frac{5 \pm \sqrt{25 + 176}}{8} = \frac{5 \pm \sqrt{201}}{8}$$
$$y_1 = \frac{5 + 14.177}{8} \approx 2.40$$
$$y_2 = \frac{5 - 14.177}{8} \approx -1.15$$

**(c)**
Find a common denominator:
$$\frac{4(x+1) - 3(x-3)}{(x-3)(x+1)}$$
$$= \frac{4x + 4 - 3x + 9}{(x-3)(x+1)}$$
$$= \frac{x + 13}{(x-3)(x+1)}$$

PastPaper.markingScheme

**(a)** [4 marks]
- M1 for factorising numerator: $(2x + 1)(x - 3)$
- M1 for factorising denominator: $(2x + 1)(2x - 1)$
- A1 for cancelling common factor $(2x+1)$
- A1 for final answer $\frac{x - 3}{2x - 1}$

**(b)** [5 marks]
- M1 for clearing fractions: $3(2y - 1) + 5(y + 2) = 2(y + 2)(2y - 1)$
- M1 for expanding correctly to form $4y^2 - 5y - 11 = 0$
- M1 for applying the quadratic formula with their $a, b, c$ values
- A1 for $y = 2.40$ (or $2.4$)
- A1 for $y = -1.15$

**(c)** [2.8 marks]
- M1 for common denominator $(x-3)(x+1)$
- M1 for expanding numerator $4(x+1) - 3(x-3)$
- A0.8 for final answer $\frac{x + 13}{(x-3)(x+1)}$ or $\frac{x+13}{x^2-2x-3}$
PastPaper.question 2 · structured_multipart
11.8 PastPaper.marks
A solid metal cone has a base radius of $6\text{ cm}$ and a perpendicular height of $8\text{ cm}$.

(a) Show that the total surface area of the cone is $96\pi\text{ cm}^2$.

(b) The cone is melted down and recast into 5 identical solid spheres. Calculate the radius of one of these spheres.

(c) Calculate the total surface area of one of these spheres.
PastPaper.showAnswers

PastPaper.workedSolution

**(a)**
First, find the slant height, $l$, of the cone using Pythagoras' theorem:
$$l = \sqrt{r^2 + h^2} = \sqrt{6^2 + 8^2} = \sqrt{36 + 64} = 10\text{ cm}$$
The curved surface area of the cone is:
$$\text{CSA} = \pi r l = \pi \times 6 \times 10 = 60\pi\text{ cm}^2$$
The area of the circular base is:
$$\text{Base Area} = \pi r^2 = \pi \times 6^2 = 36\pi\text{ cm}^2$$
Total surface area of the cone is:
$$\text{Total Area} = 60\pi + 36\pi = 96\pi\text{ cm}^2$$

**(b)**
First, calculate the volume of the cone:
$$V_{\text{cone}} = \frac{1}{3}\pi r^2 h = \frac{1}{3}\pi \times 6^2 \times 8 = 96\pi\text{ cm}^3$$
Since the cone is recast into 5 identical spheres, the volume of one sphere is:
$$V_{\text{sphere}} = \frac{96\pi}{5} = 19.2\pi\text{ cm}^3$$
The formula for the volume of a sphere is $V = \frac{4}{3}\pi R^3$. Equating these:
$$\frac{4}{3}\pi R^3 = 19.2\pi$$
$$\frac{4}{3} R^3 = 19.2$$
$$R^3 = 19.2 \times \frac{3}{4} = 14.4$$
$$R = \sqrt[3]{14.4} \approx 2.43288...\text{ cm}$$
To 3 significant figures, $R = 2.43\text{ cm}$.

**(c)**
The surface area of a sphere is given by the formula $A = 4\pi R^2$:
$$A = 4\pi \times (2.43288)^2$$
$$A = 4\pi \times 5.9189$$
$$A \approx 74.379\text{ cm}^2$$
To 3 significant figures, $A = 74.4\text{ cm}^2$.

PastPaper.markingScheme

**(a)** [3.8 marks]
- M1 for finding slant height $l = \sqrt{6^2 + 8^2} = 10$
- M1 for curved surface area formula $\pi \times 6 \times 10 = 60\pi$
- M1 for base area formula $\pi \times 6^2 = 36\pi$
- A0.8 for summing to $96\pi$ with no errors shown

**(b)** [4 marks]
- M1 for finding volume of the cone $V = 96\pi$ (or approx 301.6)
- M1 for setting $\frac{4}{3}\pi R^3 = \frac{\text{their } V}{5}$
- M1 for isolating $R^3 = 14.4$
- A1 for $2.43$ (accept 2.43 to 2.44)

**(c)** [4 marks]
- M1 for recalling formula $A = 4\pi R^2$
- M1 for substituting their radius $R$ into the formula
- A1 for $74.4$ (accept 74.3 to 74.5)
PastPaper.question 3 · structured_multipart
11.8 PastPaper.marks
A triangular plot of land $ABC$ has sides $AB = 75\text{ m}$, $BC = 110\text{ m}$ and angle $ABC = 54^\circ$.

(a) Calculate the distance $AC$. Give your answer correct to 3 significant figures.

(b) Calculate angle $ACB$. Give your answer correct to 1 decimal place.

(c) Calculate the area of the triangular plot $ABC$.
PastPaper.showAnswers

PastPaper.workedSolution

**(a)**
Using the Cosine Rule to find $AC$:
$$AC^2 = AB^2 + BC^2 - 2(AB)(BC)\cos(\angle ABC)$$
$$AC^2 = 75^2 + 110^2 - 2(75)(110)\cos(54^\circ)$$
$$AC^2 = 5625 + 12100 - 16500\cos(54^\circ)$$
$$AC^2 = 17725 - 16500(0.587785)$$
$$AC^2 = 17725 - 9698.46 = 8026.54$$
$$AC = \sqrt{8026.54} \approx 89.591\text{ m}$$
To 3 significant figures, $AC = 89.6\text{ m}$.

**(b)**
Using the Sine Rule to find angle $ACB$:
$$\frac{\sin(\angle ACB)}{AB} = \frac{\sin(\angle ABC)}{AC}$$
$$\frac{\sin(\angle ACB)}{75} = \frac{\sin(54^\circ)}{89.591}$$
$$\sin(\angle ACB) = \frac{75 \times \sin(54^\circ)}{89.591}$$
$$\sin(\angle ACB) = \frac{75 \times 0.809017}{89.591} \approx 0.67726$$
$$\angle ACB = \sin^{-1}(0.67726) \approx 42.63^\circ$$
To 1 decimal place, $\angle ACB = 42.6^\circ$.

**(c)**
Using the area of a triangle formula:
$$\text{Area} = \frac{1}{2} \times AB \times BC \times \sin(\angle ABC)$$
$$\text{Area} = \frac{1}{2} \times 75 \times 110 \times \sin(54^\circ)$$
$$\text{Area} = 4125 \times 0.809017 \approx 3337.19\text{ m}^2$$
To 3 significant figures, $\text{Area} = 3340\text{ m}^2$.

PastPaper.markingScheme

**(a)** [4.8 marks]
- M1 for writing down correct cosine rule formula
- M1 for correct substitution: $75^2 + 110^2 - 2(75)(110)\cos(54^\circ)$
- A1 for $8026.5$ or better
- A1.8 for $89.6$ (accept 89.5 to 89.7)

**(b)** [4 marks]
- M1 for correct sine rule formula
- M1 for correct substitution using their $AC$ value: $\frac{\sin(\angle ACB)}{75} = \frac{\sin(54^\circ)}{89.6}$
- A1 for $\sin(\angle ACB) \approx 0.677$
- A1 for $42.6^\circ$ (accept 42.5 to 42.7)

**(c)** [3 marks]
- M1 for correct area formula: $\frac{1}{2} a c \sin B$
- M1 for correct substitution: $\frac{1}{2} \times 75 \times 110 \times \sin(54^\circ)$
- A1 for 3340 (accept 3330 to 3340)
PastPaper.question 4 · structured_multipart
11.8 PastPaper.marks
(a) Liam invests $6500$ in a savings account. The account pays compound interest at a rate of $2.4\%$ per year.

(i) Calculate the total value of Liam’s investment at the end of 5 years. Give your answer to the nearest dollar.

(ii) Find the number of complete years it takes for the investment to be worth more than $9000$.

(b) Sophia buys a computer for $828$. This price includes a sales tax of $15\%$. Calculate the price of the computer before the sales tax was added.

(c) A car loses $12\%$ of its value each year. Find the percentage of its original value that remains after 4 years.
PastPaper.showAnswers

PastPaper.workedSolution

**(a)(i)**
Using the compound interest formula $A = P\left(1 + \frac{r}{100}\right)^t$:
$$A = 6500 \times (1.024)^5$$
$$A \approx 6500 \times 1.1258999$$
$$A \approx 7318.35$$
To the nearest dollar, the value is $7318.

**(a)(ii)**
We want to find the smallest integer $n$ such that:
$$6500 \times (1.024)^n > 9000$$
$$(1.024)^n > \frac{9000}{6500}$$
$$(1.024)^n > 1.3846$$
Taking logarithms on both sides:
$$n \log(1.024) > \log(1.3846)$$
$$n > \frac{\log(1.3846)}{\log(1.024)}$$
$$n > \frac{0.14133}{0.01030} \approx 13.72\text{ years}$$
Since $n$ must be a complete year, it takes 14 complete years.

**(b)**
Let $P$ be the original price of the computer.
$$P \times (1 + 0.15) = 828$$
$$1.15 P = 828$$
$$P = \frac{828}{1.15} = 720$$
The price before sales tax was $720.

**(c)**
Let the original value of the car be $V_0$.
Each year, the value is multiplied by $(1 - 0.12) = 0.88$.
After 4 years, the remaining value is:
$$V = V_0 \times (0.88)^4$$
$$(0.88)^4 = 0.599695$$
Expressing this as a percentage: $0.599695 \times 100\% \approx 59.97\%$.
To 3 significant figures, the remaining value is $60.0\%$.

PastPaper.markingScheme

**(a)(i)** [3 marks]
- M1 for $6500 \times 1.024^5$
- A1 for 7318.35
- A1 for 7318 (nearest dollar)

**(a)(ii)** [3.8 marks]
- M1 for writing the inequality or equation $6500 \times 1.024^n > 9000$
- M1 for trial and error showing values for $n=13$ ($8849.63$) and $n=14$ ($9062.02$), OR for using logarithms correctly
- A1.8 for 14

**(b)** [3 marks]
- M1 for $P \times 1.15 = 828$
- M1 for division $\frac{828}{1.15}$
- A1 for 720

**(c)** [2 marks]
- M1 for calculation $0.88^4$
- A1 for $60.0$ or $59.97$
PastPaper.question 5 · structured_multipart
11.8 PastPaper.marks
Triangle $T$ has vertices $A(1, 2)$, $B(4, 2)$, and $C(3, 4)$.

(a) Triangle $T$ is mapped onto triangle $U$ by a reflection in the line $y = -x$. Write down the coordinates of the vertices of triangle $U$.

(b) Triangle $T$ is mapped onto triangle $V$ by an enlargement, scale factor $2.5$, center of enlargement $(0,0)$. Find the coordinates of the vertices of triangle $V$.

(c) Triangle $T$ is mapped onto triangle $W$ by a shear, with the $x$-axis invariant and a shear factor of $2$. Find the coordinates of the vertices of triangle $W$.

(d) Write down the $2 \times 2$ matrix representing the transformation that maps triangle $T$ onto triangle $W$.
PastPaper.showAnswers

PastPaper.workedSolution

**(a)**
Reflection in the line $y = -x$ maps any point $(x, y)$ to $(-y, -x)$.
Applying this rule to each vertex:
- $A(1, 2) \to A'(-2, -1)$
- $B(4, 2) \to B'(-2, -4)$
- $C(3, 4) \to C'(-4, -3)$

**(b)**
An enlargement with scale factor $2.5$ and center $(0,0)$ multiplies each coordinate by $2.5$:
- $A(1, 2) \to A''(2.5, 5)$
- $B(4, 2) \to B''(10, 5)$
- $C(3, 4) \to C''(7.5, 10)$

**(c)**
A shear with the $x$-axis invariant and shear factor $k=2$ maps $(x, y)$ to $(x + ky, y)$, which is $(x + 2y, y)$.
- For $A(1, 2)$: $(1 + 2(2), 2) = (5, 2)$
- For $B(4, 2)$: $(4 + 2(2), 2) = (8, 2)$
- For $C(3, 4)$: $(3 + 2(4), 4) = (11, 4)$
So the vertices of $W$ are $(5, 2)$, $(8, 2)$, and $(11, 4)$.

**(d)**
The standard matrix for a shear with the $x$-axis invariant and shear factor $k$ is:
$$\begin{pmatrix} 1 & k \\ 0 & 1 \end{pmatrix}$$
Since the shear factor is $2$, the matrix is:
$$\begin{pmatrix} 1 & 2 \\ 0 & 1 \end{pmatrix}$$
We can verify this with $A(1, 2)$:
$$\begin{pmatrix} 1 & 2 \\ 0 & 1 \end{pmatrix} \begin{pmatrix} 1 \\ 2 \end{pmatrix} = \begin{pmatrix} 1(1) + 2(2) \\ 0(1) + 1(2) \end{pmatrix} = \begin{pmatrix} 5 \\ 2 \end{pmatrix}$$

PastPaper.markingScheme

**(a)** [3 marks]
- B1 for each correct point: $A'(-2, -1)$, $B'(-2, -4)$, $C'(-4, -3)$

**(b)** [3 marks]
- B1 for each correct point: $A''(2.5, 5)$, $B''(10, 5)$, $C''(7.5, 10)$

**(c)** [3 marks]
- M1 for using transformation rule $(x+2y, y)$
- A2 for all three points correct: $(5, 2)$, $(8, 2)$, and $(11, 4)$ (A1 if one error)

**(d)** [2.8 marks]
- M1 for writing a matrix of the form $\begin{pmatrix} 1 & k \\ 0 & 1 \end{pmatrix}$
- A1.8 for the correct matrix $\begin{pmatrix} 1 & 2 \\ 0 & 1 \end{pmatrix}$
PastPaper.question 6 · structured_multipart
11.8 PastPaper.marks
A cuboid $ABCD\text{-}EFGH$ has a horizontal rectangular base $ABCD$ with $AB = 12\text{ cm}$ and $BC = 5\text{ cm}$. The vertical edges $AE$, $BF$, $CG$, and $DH$ have a length of $8\text{ cm}$.

(a) Calculate the length of the diagonal $AC$ of the base.

(b) Calculate the length of the space diagonal $AG$.

(c) Calculate the angle that the diagonal $AG$ makes with the horizontal base $ABCD$.

(d) Calculate the angle that the diagonal $AG$ makes with the vertical edge $AE$.
PastPaper.showAnswers

PastPaper.workedSolution

**(a)**
The base $ABCD$ is a rectangle. Use Pythagoras' theorem in the right-angled triangle $ABC$:
$$AC^2 = AB^2 + BC^2$$
$$AC^2 = 12^2 + 5^2 = 144 + 25 = 169$$
$$AC = \sqrt{169} = 13\text{ cm}$$

**(b)**
The vertical edge $CG$ is perpendicular to the base $ABCD$, and therefore perpendicular to the line $AC$.
In the right-angled triangle $ACG$, use Pythagoras' theorem:
$$AG^2 = AC^2 + CG^2$$
$$AG^2 = 13^2 + 8^2 = 169 + 64 = 233$$
$$AG = \sqrt{233} \approx 15.264\text{ cm}$$
To 3 significant figures, $AG = 15.3\text{ cm}$.

**(c)**
The angle that $AG$ makes with the horizontal base $ABCD$ is the angle $\angle CAG$.
In the right-angled triangle $ACG$:
$$\tan(\angle CAG) = \frac{CG}{AC} = \frac{8}{13}$$
$$\angle CAG = \tan^{-1}\left(\frac{8}{13}\right) \approx \tan^{-1}(0.61538) \approx 31.607^\circ$$
To 1 decimal place, the angle is $31.6^\circ$.

**(d)**
The angle that $AG$ makes with the vertical edge $AE$ is the angle $\angle EAG$.
In the right-angled triangle $AEG$ (where $EG$ is the diagonal of the top face, which is equal to $AC = 13\text{ cm}$):
$$\tan(\angle EAG) = \frac{EG}{AE} = \frac{13}{8}$$
$$\angle EAG = \tan^{-1}\left(\frac{13}{8}\right) = \tan^{-1}(1.625) \approx 58.39^\circ$$
To 1 decimal place, the angle is $58.4^\circ$.

PastPaper.markingScheme

**(a)** [3 marks]
- M1 for $12^2 + 5^2$
- A1 for $\sqrt{169}$
- A1 for 13

**(b)** [3 marks]
- M1 for $AC^2 + 8^2$ (or $12^2 + 5^2 + 8^2$)
- A1 for $\sqrt{233}$
- A1 for 15.3

**(c)** [3 marks]
- M1 for identifying angle $\angle CAG$ and using tangent (or sine/cosine with their $AG$)
- M1 for $\tan(\angle CAG) = \frac{8}{13}$
- A1 for $31.6^\circ$ (accept 31.5 to 31.7)

**(d)** [2.8 marks]
- M1 for identifying angle $\angle EAG$ and using $\tan(\angle EAG) = \frac{13}{8}$ or alternate valid trig ratio
- A1.8 for $58.4^\circ$ (accept 58.3 to 58.5)
PastPaper.question 7 · structured_multipart
11.8 PastPaper.marks
A box contains 6 red pens, 4 blue pens, and 2 green pens.

(a) Two pens are selected at random, one after the other, without replacement.

(i) Find the probability that both pens are red.

(ii) Find the probability that the two pens are of different colors.

(b) Three pens are selected at random, one after the other, with replacement.

Find the probability that at least one of the selected pens is green.
PastPaper.showAnswers

PastPaper.workedSolution

**(a)(i)**
Total number of pens = $6 + 4 + 2 = 12$.
Probability of selecting a red pen first is $\frac{6}{12} = \frac{1}{2}$.
Since the selection is without replacement, there are now 5 red pens and 11 total pens.
Probability of selecting a second red pen is $\frac{5}{11}$.
$$P(\text{both red}) = \frac{6}{12} \times \frac{5}{11} = \frac{30}{132} = \frac{5}{22} \approx 0.227$$

**(a)(ii)**
It is easier to first find the probability that both pens are of the same color.
$$P(\text{same color}) = P(\text{both red}) + P(\text{both blue}) + P(\text{both green})$$
- $P(\text{both red}) = \frac{6}{12} \times \frac{5}{11} = \frac{30}{132}$
- $P(\text{both blue}) = \frac{4}{12} \times \frac{3}{11} = \frac{12}{132}$
- $P(\text{both green}) = \frac{2}{12} \times \frac{1}{11} = \frac{2}{132}$
$$P(\text{same color}) = \frac{30}{132} + \frac{12}{132} + \frac{2}{132} = \frac{44}{132} = \frac{1}{3}$$
Since the two pens are either the same color or different colors:
$$P(\text{different colors}) = 1 - P(\text{same color}) = 1 - \frac{1}{3} = \frac{2}{3} \approx 0.667$$

**(b)**
Since the pens are selected with replacement, the probability of selecting a green pen in any draw is constant:
$$P(\text{Green}) = \frac{2}{12} = \frac{1}{6}$$
Thus, the probability of NOT selecting a green pen in any draw is:
$$P(\text{Not Green}) = 1 - \frac{1}{6} = \frac{5}{6}$$
The probability of getting NO green pens in three selections is:
$$P(\text{no green}) = \left(\frac{5}{6}\right)^3 = \frac{125}{216}$$
The probability of getting at least one green pen is:
$$P(\text{at least one green}) = 1 - P(\text{no green}) = 1 - \frac{125}{216} = \frac{91}{216} \approx 0.421$$

PastPaper.markingScheme

**(a)(i)** [3 marks]
- M1 for product of two fractions, second denominator being 11
- M1 for $\frac{6}{12} \times \frac{5}{11}$ or equivalent
- A1 for $\frac{5}{22}$ or $0.227$ (accept $0.227$ to $0.23$)

**(a)(ii)** [4.8 marks]
- M1 for finding at least one other same-color pair: e.g., $P(\text{blue, blue}) = \frac{4}{12} \times \frac{3}{11}$
- M1 for summing same-color probabilities: $P(R,R) + P(B,B) + P(G,G)$
- M1 for subtracting their sum from 1
- A1.8 for $\frac{2}{3}$ or $0.667$ (accept $0.667$ to $0.67$)

**(b)** [4 marks]
- M1 for identifying the probability of not green on one draw is $\frac{10}{12}$ or $\frac{5}{6}$
- M1 for calculating $(\text{not green})^3 = \left(\frac{5}{6}\right)^3 = \frac{125}{216}$
- M1 for $1 - \left(\frac{5}{6}\right)^3$
- A1 for $\frac{91}{216}$ or $0.421$ (accept $0.421$ to $0.422$)
PastPaper.question 8 · structured_multipart
11.8 PastPaper.marks
A curve has the equation $y = 2x^3 - 3x^2 - 12x + 5$.

(a) Find $\frac{dy}{dx}$.

(b) Find the coordinates of the two stationary points on the curve.

(c) Determine the nature of each of these stationary points. Show all your working clearly.
PastPaper.showAnswers

PastPaper.workedSolution

**(a)**
Differentiate the curve $y = 2x^3 - 3x^2 - 12x + 5$ term-by-term with respect to $x$:
$$\frac{dy}{dx} = 3(2x^2) - 2(3x^1) - 12 + 0$$
$$\frac{dy}{dx} = 6x^2 - 6x - 12$$

**(b)**
At a stationary point, the gradient $\frac{dy}{dx} = 0$:
$$6x^2 - 6x - 12 = 0$$
Divide the entire equation by 6:
$$x^2 - x - 2 = 0$$
Factorise the quadratic:
$$(x - 2)(x + 1) = 0$$
So, the $x$-coordinates of the stationary points are $x = 2$ and $x = -1$.

Find the corresponding $y$-coordinates by substituting the $x$-values back into the original curve equation:
- For $x = 2$:
$$y = 2(2)^3 - 3(2)^2 - 12(2) + 5$$
$$y = 2(8) - 3(4) - 24 + 5 = 16 - 12 - 24 + 5 = -15$$
So, one stationary point is $(2, -15)$.

- For $x = -1$:
$$y = 2(-1)^3 - 3(-1)^2 - 12(-1) + 5$$
$$y = 2(-1) - 3(1) + 12 + 5 = -2 - 3 + 12 + 5 = 12$$
So, the other stationary point is $(-1, 12)$.

**(c)**
To find the nature of each stationary point, we can use the second derivative test.
Differentiate $\frac{dy}{dx} = 6x^2 - 6x - 12$ with respect to $x$:
$$\frac{d^2y}{dx^2} = 12x - 6$$

Now test each stationary point:
- For $x = 2$:
$$\frac{d^2y}{dx^2} = 12(2) - 6 = 24 - 6 = 18$$
Since $\frac{d^2y}{dx^2} > 0$, the point $(2, -15)$ is a **local minimum**.

- For $x = -1$:
$$\frac{d^2y}{dx^2} = 12(-1) - 6 = -12 - 6 = -18$$
Since $\frac{d^2y}{dx^2} < 0$, the point $(-1, 12)$ is a **local maximum**.

PastPaper.markingScheme

**(a)** [2 marks]
- M1 for attempting to differentiate at least one term (e.g., $6x^2$ or $-6x$)
- A1 for $6x^2 - 6x - 12$

**(b)** [5 marks]
- M1 for setting their $\frac{dy}{dx} = 0$
- M1 for factorising or solving $x^2 - x - 2 = 0$ to get $x = 2, -1$
- M1 for substituting $x = 2$ or $x = -1$ into original equation to find $y$
- A1 for $(2, -15)$
- A1 for $(-1, 12)$

**(c)** [4.8 marks]
- M1 for finding the second derivative: $12x - 6$
- M1 for substituting $x = 2$ into their $\frac{d^2y}{dx^2}$ and concluding local minimum because it is positive
- M1 for substituting $x = -1$ into their $\frac{d^2y}{dx^2}$ and concluding local maximum because it is negative
- A1.8 for fully correct working and conclusions
PastPaper.question 9 · structured_multipart
12 PastPaper.marks
A solid trophy is made from a cylinder and a cone.
The cylinder has radius \(5\text{ cm}\) and height \(12\text{ cm}\).
The cone has base radius \(5\text{ cm}\) and slant height \(13\text{ cm}\).

(a) (i) Show that the height of the cone is \(12\text{ cm}\).
(ii) Calculate the total volume of the trophy.
(iii) Calculate the total surface area of the trophy (including its base).

(b) The trophy is melted down and recast into solid spheres, each of radius \(1.5\text{ cm}\).
Calculate the maximum number of complete spheres that can be made.
PastPaper.showAnswers

PastPaper.workedSolution

**(a) (i)**
Using Pythagoras' theorem in the right-angled triangle formed by the radius, height, and slant height of the cone:
\(h_{\text{cone}} = \sqrt{l^2 - r^2}\)
\(h_{\text{cone}} = \sqrt{13^2 - 5^2} = \sqrt{169 - 25} = \sqrt{144} = 12\text{ cm}\).

**(a) (ii)**
Total volume, \(V = V_{\text{cylinder}} + V_{\text{cone}}\)
\(V = \pi r^2 h_{\text{cylinder}} + \frac{1}{3}\pi r^2 h_{\text{cone}}\)
\(V = \pi \times 5^2 \times 12 + \frac{1}{3}\pi \times 5^2 \times 12\)
\(V = 300\pi + 100\pi = 400\pi \approx 1256.6\text{ cm}^3 \approx 1260\text{ cm}^3\) (to 3 s.f.).

**(a) (iii)**
Total surface area, \(A = A_{\text{base}} + A_{\text{curved, cylinder}} + A_{\text{curved, cone}}\)
\(A = \pi r^2 + 2\pi r h_{\text{cylinder}} + \pi r l\)
\(A = \pi \times 5^2 + 2\pi \times 5 \times 12 + \pi \times 5 \times 13\)
\(A = 25\pi + 120\pi + 65\pi = 210\pi \approx 659.7\text{ cm}^2 \approx 660\text{ cm}^2\) (to 3 s.f.).

**(b)**
Volume of one sphere:
\(V_{\text{sphere}} = \frac{4}{3}\pi r^3 = \frac{4}{3}\pi \times 1.5^3 = 4.5\pi \approx 14.137\text{ cm}^3\).
Number of spheres \(N = \frac{400\pi}{4.5\pi} = \frac{400}{4.5} \approx 88.89\).
Maximum number of complete spheres is \(88\).

PastPaper.markingScheme

**(a)(i)**
M1: For using Pythagoras' theorem: \(\sqrt{13^2 - 5^2}\) or \(h^2 + 5^2 = 13^2\)
A1: Correctly showing 12

**(a)(ii)**
M1: For volume of cylinder: \(\pi \times 5^2 \times 12\) [\(300\pi\)]
M1: For volume of cone: \(\frac{1}{3} \pi \times 5^2 \times 12\) [\(100\pi\)]
A1: For 1260 or 1256.6 to 1257

**(a)(iii)**
M1: For area of base: \(\pi \times 5^2\) [\(25\pi\)]
M1: For curved area of cylinder: \(2 \pi \times 5 \times 12\) [\(120\pi\)]
M1: For curved area of cone: \(\pi \times 5 \times 13\) [\(65\pi\)]
A1: For 660 or 659.7 to 660

**(b)**
M1: For volume of one sphere: \(\frac{4}{3} \pi \times 1.5^3\) [\(4.5\pi\) or 14.1 to 14.14]
M1: For dividing total volume by volume of one sphere
A1: For 88 (must be integer)
PastPaper.question 10 · structured_multipart
12 PastPaper.marks
A cyclist rides a distance of \(36\text{ km}\) at an average speed of \(x\text{ km/h}\).

(a) Write down an expression, in terms of \(x\), for the time taken for this outward journey.

(b) On the return journey, the cyclist's average speed is increased by \(3\text{ km/h}\).
Write down an expression, in terms of \(x\), for the time taken for the return journey.

(c) The time taken for the return journey is \(24\text{ minutes}\) less than the time taken for the outward journey.

(i) Write down an equation in \(x\) and show that it simplifies to \(x^2 + 3x - 270 = 0\).
(ii) Solve the equation \(x^2 + 3x - 270 = 0\).
(iii) Calculate the total time taken for the entire round trip. Give your answer in hours and minutes.
PastPaper.showAnswers

PastPaper.workedSolution

**(a)**
Time \(= \frac{\text{Distance}}{\text{Speed}} = \frac{36}{x}\) hours.

**(b)**
New speed \(= x + 3\text{ km/h}\).
Time taken \(= \frac{36}{x+3}\) hours.

**(c) (i)**
\(24\text{ minutes} = \frac{24}{60}\text{ hours} = \frac{2}{5}\text{ hours} = 0.4\text{ hours}\).
Therefore, the equation is:
\[\frac{36}{x} - \frac{36}{x+3} = \frac{2}{5}\]
Multiply the entire equation by \(5x(x+3)\) to clear the denominators:
\[5 \times 36(x+3) - 5 \times 36x = 2x(x+3)\]
\[180(x+3) - 180x = 2x^2 + 6x\]
\[180x + 540 - 180x = 2x^2 + 6x\]
\[540 = 2x^2 + 6x\]
Divide the entire equation by 2:
\[270 = x^2 + 3x\]
Rearranging gives:
\[x^2 + 3x - 270 = 0\]

**(c) (ii)**
Factoring \(x^2 + 3x - 270 = 0\):
We look for two numbers that multiply to \(-270\) and add to \(3\). These are \(18\) and \(-15\).
\[(x + 18)(x - 15) = 0\]
Thus, \(x = 15\) or \(x = -18\).

**(c) (iii)**
Since speed cannot be negative, \(x = 15\).
Outward time \(= \frac{36}{15} = 2.4\text{ hours} = 2\text{ hours and } 24\text{ minutes}\).
Return time \(= \frac{36}{15+3} = \frac{36}{18} = 2\text{ hours}\).
Total time taken \(= 2.4 + 2 = 4.4\text{ hours} = 4\text{ hours and } 24\text{ minutes}\).

PastPaper.markingScheme

**(a)**
B1: For \(\frac{36}{x}\)

**(b)**
B1: For \(\frac{36}{x+3}\)

**(c)(i)**
M1: For converting 24 minutes to hours: \(\frac{24}{60}\) or \(0.4\) or \(\frac{2}{5}\)
M1: For setting up equation: \(\frac{36}{x} - \frac{36}{x+3} = \frac{24}{60}\) (or equivalent)
M1: For multiplying by common denominator to clear fractions: \(5 \times 36(x+3) - 180x = 2x(x+3)\) (or equivalent)
A1: For completing the simplification to show \(x^2 + 3x - 270 = 0\) with no errors

**(c)(ii)**
M1: For factoring \((x-15)(x+18)\) or correct use of quadratic formula with at most one sign error
A1: For \(x = 15\)
A1: For \(x = -18\)

**(c)(iii)**
M1: For substituting their positive \(x\) value into their time expressions
M1: For adding both times: \(2.4 + 2\)
A1: For \(4\text{ hours } 24\text{ minutes}\)
PastPaper.question 11 · structured_multipart
12 PastPaper.marks
Three ports, \(A\), \(B\), and \(C\), are situated such that \(B\) is \(18\text{ km}\) from \(A\) on a bearing of \(075^\circ\).
Port \(C\) is \(25\text{ km}\) from \(A\). The bearing of \(C\) from \(A\) is \(140^\circ\).

(a) Calculate the distance between \(B\) and \(C\).

(b) Calculate the bearing of \(C\) from \(B\).

(c) A boat sails from \(A\) directly to the nearest point on the line \(BC\).
Calculate the shortest distance from \(A\) to the line \(BC\).
PastPaper.showAnswers

PastPaper.workedSolution

**(a)**
First, find the angle \(\angle BAC\):
\(\angle BAC = 140^\circ - 75^\circ = 65^\circ\).
Using the Cosine Rule to find \(BC\):
\(BC^2 = AB^2 + AC^2 - 2(AB)(AC)\cos(\angle BAC)\)
\(BC^2 = 18^2 + 25^2 - 2(18)(25)\cos(65^\circ)\)
\(BC^2 = 324 + 625 - 900\cos(65^\circ)\)
\(BC^2 = 949 - 900 \times 0.422618 = 949 - 380.356 = 568.644\)
\(BC = \sqrt{568.644} \approx 23.846 \approx 23.8\text{ km}\) (to 3 s.f.).

**(b)**
Using the Sine Rule to find \(\angle ABC\):
\(\frac{\sin(\angle ABC)}{AC} = \frac{\sin(\angle BAC)}{BC}\)
\(\sin(\angle ABC) = \frac{25 \sin(65^\circ)}{23.846} \approx \frac{22.6577}{23.846} \approx 0.95017\)
\(\angle ABC = \sin^{-1}(0.95017) \approx 71.84^\circ\).
Let's determine the bearing of \(C\) from \(B\).
Draw a North-South line at both \(A\) and \(B\).
The angle between the South line at \(B\) and the line \(BA\) is \(75^\circ\) (alternate angles to the North-bearing line at \(A\)).
Since the angle \(\angle ABC = 71.84^\circ\) is less than \(75^\circ\), the line \(BC\) is to the right of the South line by \(75^\circ - 71.84^\circ = 3.16^\circ\) (going west of south).
More precisely, the South direction is at \(180^\circ\). The direction of \(BA\) from \(B\) is \(75^\circ + 180^\circ = 255^\circ\).
Subtracting \(\angle ABC = 71.84^\circ\) from \(255^\circ\) gives:
Bearing of \(C\) from \(B = 255^\circ - 71.84^\circ = 183.16^\circ \approx 183.2^\circ\) (or \(183^\circ\) to 3 s.f.).

**(c)**
The shortest distance \(d\) from \(A\) to the line \(BC\) is the perpendicular distance from \(A\) to \(BC\).
We can find this using the area of triangle \(ABC\):
\(\text{Area} = \frac{1}{2} \times AB \times AC \times \sin(\angle BAC) = \frac{1}{2} \times 18 \times 25 \times \sin(65^\circ) \approx 203.92\text{ km}^2\).
Also,
\(\text{Area} = \frac{1}{2} \times BC \times d\)
\(203.92 = \frac{1}{2} \times 23.846 \times d\)
\(d = \frac{2 \times 203.92}{23.846} \approx 17.1025 \approx 17.1\text{ km}\) (to 3 s.f.).

PastPaper.markingScheme

**(a)**
M1: For \(\angle BAC = 65^\circ\) seen or used
M1: For substituting correctly into Cosine Rule: \(18^2 + 25^2 - 2(18)(25)\cos(65^\circ)\)
A1: For \(568.6\) or \(569\)
A1: For \(23.8\) or \(23.84\) to \(23.85\)

**(b)**
M1: For using Sine Rule or Cosine Rule to find \(\angle ABC\)
M1: For \(\angle ABC \approx 71.8^\circ\) (or \(71.84^\circ\))
M1: For using back bearing or alternate angles to find South-related angle at \(B\): e.g. \(75^\circ\) or \(255^\circ\)
M1: For \(255 - \text{their } 71.8\) or \(180 + (75 - \text{their } 71.8)\)
A1: For \(183.2\) or \(183\) (accept answers in range \(183\) to \(183.3\))

**(c)**
M1: For finding area of triangle: \(\frac{1}{2} \times 18 \times 25 \times \sin(65^\circ)\) [\(203.9\)]
M1: For equating area to \(\frac{1}{2} \times BC \times d\)
A1: For \(17.1\) or \(17.10\) to \(17.11\)

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