An original Thinka practice paper modelled on the structure and difficulty of the Jun 2022 OCR GCSE Mathematics - J560 paper. Not affiliated with or reproduced from OCR.
Section A: Procedural Fluency & Core Concepts
Answer all questions. Show clear working where required.
14 Question · 31 marks
Question 1 · short-answer
2 marks
Simplify.
\(6a - 2b + 3a + 7b\)
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Worked solution
Group like terms together:
\(6a + 3a = 9a\)
\(-2b + 7b = +5b\)
Combining the terms gives \(9a + 5b\).
Marking scheme
B1 for 9a or +5b seen in the final expression B1 for 9a + 5b as final answer
Question 2 · short-answer
2 marks
Work out 15% of £340.
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Worked solution
Method 1 (multiplier): \(0.15 \times 340 = 51\)
Method 2 (chunking): \(10\%\text{ of } 340 = 34\) \(5\%\text{ of } 340 = 17\) \(15\%\text{ of } 340 = 34 + 17 = 51\)
Answer is £51.
Marking scheme
M1 for 340 × 0.15 oe or for a complete correct chunking method (e.g. 10% = 34 and 5% = 17) A1 for 51
Question 3 · short-answer
1 marks
Write 0.000305 in standard form.
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Worked solution
To write 0.000305 in standard form \(A \times 10^n\), where \(1 \le A < 10\):
Move the decimal point 4 places to the right to get \(3.05\).
Since the original number is less than 1, the power is negative: \(3.05 \times 10^{-4}\).
Marking scheme
B1 for 3.05 × 10^-4 (condone 3.05 · 10^-4)
Question 4 · short-answer
2 marks
Share £84 in the ratio \(3 : 4\).
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M1 for 84 ÷ (3 + 4) or 84 ÷ 7 (soi by 12) A1 for £36 and £48 in the correct order (accept 36 : 48 or 36, 48)
Question 5 · Short recall / 1-2 mark routine computation
2 marks
Find the lowest common multiple (LCM) of 12 and 15.
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Worked solution
Multiples of 12: 12, 24, 36, 48, 60, 72, ... Multiples of 15: 15, 30, 45, 60, 75, ... The lowest common multiple is 60.
Marking scheme
M1 for listing multiples of both 12 and 15 with at least 3 multiples of each, or correct prime factor trees/decomposition (\(12 = 2^2 \times 3\), \(15 = 3 \times 5\)) A1 for 60
Question 6 · Short recall / 1-2 mark routine computation
2 marks
Simplify.
\(4p + 7q - 9p + 2q\)
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B1 for \(-5p\) or \(+9q\) in a two-term linear expression B1 for \(-5p + 9q\) or \(9q - 5p\) as final answer
Question 7 · Short recall / 1-2 mark routine computation
1 marks
Work out 15% of £140.
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Worked solution
10% of £140 = £14 5% of £140 = £7 15% of £140 = 14 + 7 = £21.
Marking scheme
B1 for 21 (condone £21)
Question 8 · Short recall / 1-2 mark routine computation
1 marks
Write 0.000308 in standard form.
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Worked solution
Move the decimal point 4 places to the right to obtain a number between 1 and 10: 3.08. Since the original number is less than 1, the index is negative: \(3.08 \times 10^{-4}\).
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Worked solution
1. Multiply the numerical parts: \(2.4 \times 7.5 = 18\)
2. Multiply the powers of 10: \(10^5 \times 10^{-2} = 10^{5 + (-2)} = 10^3\)
3. Combine and convert to standard form: \(18 \times 10^3 = (1.8 \times 10^1) \times 10^3 = 1.8 \times 10^4\)
Marking scheme
M1 for \(2.4 \times 7.5 = 18\) or \(10^5 \times 10^{-2} = 10^3\) or \(240000 \times 0.075\) M1 for \(18 \times 10^3\) or \(18000\) seen A1 for \(1.8 \times 10^4\)
Question 13 · free-response
3 marks
\(y\) is inversely proportional to \(x\). \(y = 12\) when \(x = 5\).
Find the value of \(y\) when \(x = 15\).
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Worked solution
Since \(y\) is inversely proportional to \(x\): \[y = \frac{k}{x}\] Substitute \(x = 5\) and \(y = 12\) to find the constant of proportionality \(k\): \[12 = \frac{k}{5} \implies k = 12 \times 5 = 60\] Substitute \(x = 15\) into the formula: \[y = \frac{60}{15} = 4\]
Marking scheme
M1 for \(y = \frac{k}{x}\) or \(k = 12 \times 5\) soi by 60 M1 for \(y = \frac{\text{their } 60}{15}\) A1 for 4
Question 14 · free-response
3 marks
In a sale, the normal price of a bicycle is reduced by \(15\%\). The sale price of the bicycle is \(£442\).
Work out the normal price of the bicycle.
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Worked solution
The sale price corresponds to \(100\% - 15\% = 85\%\) of the normal price.
Answer all questions. Full method must be shown for all contextual problems.
9 Question · 42 marks
Question 1 · structured
5 marks
Priya and Rowan organize a charity event. All money raised is shared between Charity A and Charity B in the ratio \(3 : 5\).
Charity B receives £420 more than Charity A. Of the total money received by Charity A, 35% is spent on administrative costs and the rest is spent on educational books.
Work out the amount of money spent on educational books. You must show your working.
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Worked solution
1. Find the value of 1 ratio part: Difference in parts = \(5 - 3 = 2\) parts. \(2\text{ parts} = £420\) \(1\text{ part} = 420 \div 2 = £210\).
2. Calculate the total money received by Charity A: \(\text{Charity A} = 3 \times 210 = £630\).
3. Calculate the percentage and amount spent on educational books: Percentage on books = \(100\% - 35\% = 65\%\). \(\text{Amount on books} = 0.65 \times 630 = £409.50\).
Marking scheme
M1 for \(5 - 3 = 2\) parts seen or implied by \(420 \div 2\) A1 for finding 1 part = 210 M1 for \(3 \times 210\) or 630 M1 for \(0.65 \times \text{their } 630\) or \(\text{their } 630 - (0.35 \times \text{their } 630)\) oe A1 for £409.50 (condone 409.5)
Question 2 · structured
5 marks
A solid metal component is formed by taking a solid cylinder of radius \(4\text{ cm}\) and height \(15\text{ cm}\), and hollowing out a cone of the same radius \(4\text{ cm}\) and height \(9\text{ cm}\) from one end.
The metal has a density of \(7.8\text{ g/cm}^3\).
Work out the mass of the component in kilograms. Give your answer correct to 2 decimal places.
[The volume of a cone with radius \(r\) and height \(h\) is \(V = \frac{1}{3}\pi r^2 h\).]
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Worked solution
1. Find the volume of the cylinder: \(V_{\text{cylinder}} = \pi r^2 h = \pi \times 4^2 \times 15 = 240\pi \approx 753.982\text{ cm}^3\).
2. Find the volume of the cone: \(V_{\text{cone}} = \frac{1}{3}\pi r^2 h = \frac{1}{3} \times \pi \times 4^2 \times 9 = 48\pi \approx 150.796\text{ cm}^3\).
3. Find the volume of the remaining solid: \(V = 240\pi - 48\pi = 192\pi \approx 603.186\text{ cm}^3\).
4. Calculate the mass in grams: \(\text{Mass} = \text{Density} \times \text{Volume} = 7.8 \times 192\pi \approx 4704.85\text{ g}\).
5. Convert to kilograms and round to 2 decimal places: \(\text{Mass in kg} = 4704.85 \div 1000 = 4.70485\text{ kg} \approx 4.70\text{ kg}\).
Marking scheme
M1 for volume of cylinder \(\pi \times 4^2 \times 15\) soi \(240\pi\) or 753.98... M1 for volume of cone \(\frac{1}{3}\pi \times 4^2 \times 9\) soi \(48\pi\) or 150.79... M1 for subtracting cone volume from cylinder volume soi \(192\pi\) or 603.18... M1 for their volume \(\times 7.8 \div 1000\) oe A1 for 4.70 (accept answers in range 4.70 to 4.71)
Question 3 · structured
4 marks
The intensity of light, \(I\) lux, received from a lamp is inversely proportional to the square of the distance, \(d\) metres, from the lamp. When \(d = 3\text{ m}\), \(I = 80\text{ lux}\).
(a) Work out the distance \(d\) when the intensity is \(45\text{ lux}\). (b) Describe what happens to the intensity of light when the distance from the lamp is halved.
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Worked solution
(a) Since \(I \propto \frac{1}{d^2}\), we have \(I = \frac{k}{d^2}\). Substitute \(d = 3\) and \(I = 80\): \(80 = \frac{k}{3^2} \implies 80 = \frac{k}{9} \implies k = 720\).
So the formula is \(I = \frac{720}{d^2}\). When \(I = 45\): \(45 = \frac{720}{d^2} \implies d^2 = \frac{720}{45} = 16\). Since distance must be positive, \(d = \sqrt{16} = 4\text{ m}\).
(b) If distance \(d\) is replaced by \(\frac{d}{2}\), the new intensity is: \(I_{\text{new}} = \frac{k}{\left(\frac{d}{2}\right)^2} = \frac{k}{\frac{d^2}{4}} = 4 \times \frac{k}{d^2} = 4I\). Therefore, the intensity is quadrupled (multiplied by 4).
Marking scheme
(a) M1 for \(I = \frac{k}{d^2}\) oe or \(80 \times 3^2\) A1 for \(k = 720\) A1 for \(d = 4\) (b) B1 for stating it increases by a factor of 4 / quadruples / is 4 times greater oe
Question 4 · structured
4 marks
Every morning, Alex travels to work either by cycling or by taking the bus.
• The probability that Alex cycles is \(0.7\). • When Alex cycles, the probability of arriving late is \(0.08\). • When Alex takes the bus, the probability of arriving late is \(0.25\).
Work out the probability that Alex arrives on time on a randomly chosen day.
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Worked solution
1. Identify the probability of taking the bus: \(P(\text{Bus}) = 1 - 0.7 = 0.3\).
2. Find the on-time probability for each mode of transport: - If cycling: \(P(\text{On time} \mid \text{Cycle}) = 1 - 0.08 = 0.92\). - If taking bus: \(P(\text{On time} \mid \text{Bus}) = 1 - 0.25 = 0.75\).
3. Calculate the combined probability of arriving on time: \(P(\text{Cycle and On time}) = 0.7 \times 0.92 = 0.644\) \(P(\text{Bus and On time}) = 0.3 \times 0.75 = 0.225\)
4. Total probability on time: \(P(\text{On time}) = 0.644 + 0.225 = 0.869\).
Marking scheme
B1 for \(P(\text{Bus}) = 0.3\) or \(P(\text{On time} \mid \text{Cycle}) = 0.92\) or \(P(\text{On time} \mid \text{Bus}) = 0.75\) soi M1 for \(0.7 \times 0.92\) soi by 0.644 OR \(0.3 \times 0.75\) soi by 0.225 M1 for \((0.7 \times 0.92) + (0.3 \times 0.75)\) oe OR for \(1 - [(0.7 \times 0.08) + (0.3 \times 0.25)] = 1 - [0.056 + 0.075] = 1 - 0.131\) A1 for 0.869 oe (e.g. 86.9% or \(\frac{869}{1000}\))
Question 5 · free_response
5 marks
A solid metal cylinder has radius \(3\text{ cm}\) and height \(8\text{ cm}\). A cylindrical hole of radius \(1\text{ cm}\) is drilled through the centre of the cylinder from top to bottom.
The remaining metal is melted down and recast to make identical solid spheres, each of radius \(1.5\text{ cm}\).
Work out the maximum number of complete spheres that can be made. You must show your working.
[The volume \(V\) of a cylinder with radius \(r\) and height \(h\) is \(V = \pi r^2 h\).] [The volume \(V\) of a sphere with radius \(r\) is \(V = \frac{4}{3}\pi r^3\).]
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Worked solution
1. Volume of the outer cylinder: \[ V_1 = \pi \times 3^2 \times 8 = 72\pi \approx 226.19\text{ cm}^3 \]
2. Volume of the cylindrical hole: \[ V_2 = \pi \times 1^2 \times 8 = 8\pi \approx 25.13\text{ cm}^3 \]
5. Maximum number of complete spheres: \[ \frac{64\pi}{4.5\pi} = \frac{64}{4.5} = \frac{128}{9} \approx 14.22 \] Since only complete spheres can be made, the maximum number is 14.
Marking scheme
M1 for \(\pi \times 3^2 \times 8\) [soi by \(72\pi\) or \(226.19\ldots\)] M1 for \(\pi \times 1^2 \times 8\) [soi by \(8\pi\) or \(25.13\ldots\)] M1 for \(\frac{4}{3} \times \pi \times 1.5^3\) [soi by \(4.5\pi\) or \(14.13\ldots\) to \(14.14\)] M1 for their remaining volume \(\div\) their sphere volume [soi by \(14.22\ldots\)] A1 for 14 cao
Question 6 · free_response
4 marks
A community garden has a total area of \(360\text{ m}^2\). The garden is divided into three sections: a lawn, a flower section, and a vegetable patch.
• The lawn accounts for \(40\%\) of the total area. • The remaining area is shared between the vegetable patch and the flower section in the ratio \(3 : 5\). • A packet of flower seeds costs \(£4.75\) and covers an area of \(12\text{ m}^2\). • Whole packets of seeds must be purchased.
Calculate the total cost to buy enough packets of flower seeds to cover the flower section completely. You must show your working.
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Worked solution
1. Find the area of the lawn: \[ \text{Lawn area} = 0.40 \times 360 = 144\text{ m}^2 \]
2. Find the remaining area for vegetables and flowers: \[ 360 - 144 = 216\text{ m}^2 \]
3. Divide the remaining area in the ratio \(3 : 5\): \[ \text{Total parts} = 3 + 5 = 8 \] \[ 1\text{ part} = 216 \div 8 = 27\text{ m}^2 \] \[ \text{Flower area} = 5 \times 27 = 135\text{ m}^2 \]
4. Find the number of packets of seeds needed: \[ 135 \div 12 = 11.25 \] Since whole packets must be purchased, 12 packets are needed.
5. Calculate the total cost: \[ 12 \times £4.75 = £57 \]
Marking scheme
M1 for \(360 - (0.40 \times 360)\) oe [soi by 216] M1 for their \(216 \div (3 + 5) \times 5\) oe [soi by 135] M1 for their \(135 \div 12\) [soi by \(11.25\)] rounded up to 12 packets A1 for 57 or 57.00 cao
Question 7 · free-response
5 marks
A delivery drone travels in a straight line from a depot to a drop-off point. The journey takes 40 seconds in total. - The drone accelerates uniformly from rest ( = 0\text{ s}, v = 0\text{ m/s}) to a speed of 12 m/s in 10 seconds. - It then travels at a constant speed of 12 m/s for 15 seconds. - Finally, it decelerates uniformly to rest over the remaining 15 seconds.
(a) Work out the acceleration of the drone in the first 10 seconds. (b) Work out the total distance travelled by the drone in the 40 seconds. (c) Work out the average speed of the drone for the whole journey.
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Worked solution
(a) Acceleration is given by the gradient of the velocity-time graph: \[ \text{Acceleration} = \frac{\text{Change in velocity}}{\text{Time taken}} = \frac{12 - 0}{10} = 1.2\text{ m/s}^2 \]
(b) The distance travelled is the total area under the velocity-time graph. The shape is a trapezium with parallel sides of length \(b_1 = 15\text{ s}\) (from \(t=10\) to \(t=25\)) and \(b_2 = 40\text{ s}\), and height \(h = 12\text{ m/s}\): \[ \text{Area} = \frac{1}{2}(a + b)h = \frac{1}{2}(15 + 40) \times 12 = \frac{1}{2} \times 55 \times 12 = 330\text{ m} \] Alternatively, split into three sections: - Triangle 1 (0 to 10 s): \(\frac{1}{2} \times 10 \times 12 = 60\text{ m}\) - Rectangle (10 to 25 s): \(15 \times 12 = 180\text{ m}\) - Triangle 2 (25 to 40 s): \(\frac{1}{2} \times 15 \times 12 = 90\text{ m}\) Total distance \(= 60 + 180 + 90 = 330\text{ m}\).
(c) Average speed is given by: \[ \text{Average speed} = \frac{\text{Total distance}}{\text{Total time}} = \frac{330}{40} = 8.25\text{ m/s} \]
Marking scheme
(a) [1 mark] B1 for 1.2 or \(\frac{6}{5}\) oe
(b) [2 marks] M1 for a complete method to find the area under the graph, e.g. \(\frac{1}{2}(15 + 40) \times 12\) or \(\frac{1}{2}(10)(12) + (15)(12) + \frac{1}{2}(15)(12)\) soi by two correct sub-areas (60, 180, or 90) A1 for 330
(c) [2 marks] M1 for \(\text{their } 330 \div 40\) A1 for 8.25 or \(\frac{33}{4}\) oe (FT their distance)
Question 8 · free-response
5 marks
The equation of a curve is \(y = x^2 - 4x - 5\).
(a) Find the coordinates of the points where the curve crosses the \(x\)-axis. (b) Find the coordinates of the turning point of the curve. (c) Write down the equation of the line of symmetry of the curve.
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Worked solution
(a) Set \(y = 0\): \[ x^2 - 4x - 5 = 0 \] Factorise the quadratic: \[ (x - 5)(x + 1) = 0 \] So \(x = 5\) or \(x = -1\). The coordinates are \((-1, 0)\) and \((5, 0)\).
(b) By symmetry, the turning point occurs halfway between the \(x\)-intercepts: \[ x = \frac{-1 + 5}{2} = 2 \] Substitute \(x = 2\) into the curve's equation: \[ y = (2)^2 - 4(2) - 5 = 4 - 8 - 5 = -9 \] So the coordinates of the turning point are \((2, -9)\).
(c) The line of symmetry is the vertical line passing through the turning point: \[ x = 2 \]
Marking scheme
(a) [2 marks] M1 for factorising into \((x - 5)(x + 1)\) or use of the quadratic formula \(\frac{4 \pm \sqrt{(-4)^2 - 4(1)(-5)}}{2}\) A1 for \((-1, 0)\) and \((5, 0)\) or \(x = -1, x = 5\)
(b) [2 marks] M1 for finding \(x = 2\) (midpoint of roots or \(-\frac{b}{2a}\)) and substituting into the equation A1 for \((2, -9)\)
(c) [1 mark] B1 for \(x = 2\) oe
Question 9 · free-response
5 marks
Line \(L_1\) passes through the points \((-2, -11)\) and \((4, 7)\).
(a) Find the gradient of line \(L_1\). (b) Line \(L_2\) is parallel to line \(L_1\) and passes through the point \((3, 2)\). Find the equation of line \(L_2\). Give your answer in the form \(y = mx + c\).
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Worked solution
(a) The gradient \(m\) is calculated as: \[ m = \frac{y_2 - y_1}{x_2 - x_1} = \frac{7 - (-11)}{4 - (-2)} = \frac{18}{6} = 3 \]
(b) Parallel lines have the same gradient, so line \(L_2\) has gradient \(m = 3\). The equation of line \(L_2\) can be written as \(y = 3x + c\). Substitute the coordinates of the point \((3, 2)\): \[ 2 = 3(3) + c \] \[ 2 = 9 + c \] \[ c = 2 - 9 = -7 \] Thus, the equation of the line is: \[ y = 3x - 7 \]
Marking scheme
(a) [2 marks] M1 for \(\frac{7 - (-11)}{4 - (-2)}\) oe A1 for 3
(b) [3 marks] M1 for using gradient \(m = 3\) or their (a) in \(y = mx + c\) or \(y - y_1 = m(x - x_1)\) M1 for substituting \((3, 2)\) into their linear equation A1 for \(y = 3x - 7\) (FT their gradient for M marks only)
Section C: Advanced Problem Solving & Synthesis
Answer all questions. Present complete analytical proofs and exact expressions where demanded.
5 Question · 26 marks
Question 1 · free_text
5 marks
Solve the inequality \[2x^2 - 7x - 15 \leqslant 0\] Give your answer using set notation. You must show your working.
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Worked solution
First, find the critical values by solving the corresponding quadratic equation: \[2x^2 - 7x - 15 = 0\] Factorise the quadratic expression: \[(2x + 3)(x - 5) = 0\] This gives critical values of: \[x = -\frac{3}{2} = -1.5 \quad \text{and} \quad x = 5\] Since we require the quadratic to be less than or equal to 0 (\leqslant 0), the solution lies between and includes the two critical values: \[-1.5 \leqslant x \leqslant 5\] Expressing this in set notation gives: \[\{x : -1.5 \leqslant x \leqslant 5\}\]
Marking scheme
M2 for \((2x + 3)(x - 5)\) or correct use of the quadratic formula \(\frac{7 \pm \sqrt{(-7)^2 - 4(2)(-15)}}{2(2)}\) (M1 for brackets that expand to give two correct terms or quadratic formula with at most one error) B1 for critical values \(-1.5\) (or \(-\frac{3}{2}\)) and \(5\) B1 for \(-1.5 \leqslant x \leqslant 5\) (or \(-\frac{3}{2} \leqslant x \leqslant 5\)) with correct working B1 for fully correct set notation \(\{x : -1.5 \leqslant x \leqslant 5\}\) (Award SC2 for \(\{x : -1.5 \leqslant x \leqslant 5\}\) with no or insufficient working)
Question 2 · free_text
5 marks
Simplify fully. \[\frac{2x^2 + 5x - 12}{6x^2 - 7x - 3}\] You must show your working.
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Worked solution
Factorise the numerator: \[2x^2 + 5x - 12 = (2x - 3)(x + 4)\] Factorise the denominator: \[6x^2 - 7x - 3 = (2x - 3)(3x + 1)\] Substitute the factorised expressions into the fraction: \[\frac{(2x - 3)(x + 4)}{(2x - 3)(3x + 1)}\] Cancel the common factor \((2x - 3)\): \[\frac{x + 4}{3x + 1}\]
Marking scheme
M2 for factorising numerator as \((2x - 3)(x + 4)\) (M1 for brackets that expand to give two correct terms of \(2x^2 + 5x - 12\)) AND M2 for factorising denominator as \((2x - 3)(3x + 1)\) (M1 for brackets that expand to give two correct terms of \(6x^2 - 7x - 3\)) AND A1 for \(\frac{x + 4}{3x + 1}\) final answer
Question 3 · free_text
5 marks
Solve the inequality \[6x^2 + 7x > 5\] Give your answer using set notation. You must show your working.
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Worked solution
Rearrange the inequality to make the right-hand side 0: \[6x^2 + 7x - 5 > 0\] Factorise the quadratic expression: \[(2x - 1)(3x + 5) > 0\] Find the critical values: \[2x - 1 = 0 \implies x = \frac{1}{2} = 0.5\] \[3x + 5 = 0 \implies x = -\frac{5}{3}\] Since we require the quadratic expression to be greater than 0 (\(> 0\)), the solutions lie outside the critical values: \[x < -\frac{5}{3} \quad \text{or} \quad x > \frac{1}{2}\] In set notation, this is written as: \[\{x : x < -\frac{5}{3}\} \cup \{x : x > \frac{1}{2}\}\]
Marking scheme
M1 for rearranging to \(6x^2 + 7x - 5 > 0\) or \(6x^2 + 7x - 5 = 0\) M1 for factorising as \((2x - 1)(3x + 5)\) or using formula with at most one error B1 for critical values \(-\frac{5}{3}\) and \(\frac{1}{2}\) (or \(0.5\)) B1 for \(x < -\frac{5}{3}\) or \(x > \frac{1}{2}\) (accept with 'and') B1 for fully correct set notation \(\{x : x < -\frac{5}{3}\} \cup \{x : x > \frac{1}{2}\}\) (also accept \(\{x : x < -\frac{5}{3} \text{ or } x > 0.5\}\)) (Award SC2 for correct final set notation answer with no or insufficient working)
Question 4 · free-response
5 marks
A circle has centre at the origin \(O\) and equation \(x^2 + y^2 = 45\).
The straight line \(L\) is the tangent to the circle at the point \(P(3, 6)\). Line \(L\) intersects the \(x\)-axis at point \(A\) and the \(y\)-axis at point \(B\).
Work out the area of triangle \(OAB\). You must show your working.
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Worked solution
1. Find the gradient of the radius \(OP\): \[\text{Gradient of } OP = \frac{6 - 0}{3 - 0} = 2\]
2. Find the gradient of the tangent line \(L\): Since the tangent is perpendicular to the radius, \[\text{Gradient of } L = -\frac{1}{2}\]
3. Find the equation of line \(L\): Using the point \(P(3, 6)\): \[y - 6 = -\frac{1}{2}(x - 3)\] \[y = -\frac{1}{2}x + 7.5\]
4. Determine the intercepts \(A\) and \(B\): - At point \(B\) on the \(y\)-axis, \(x = 0\): \[y = 7.5 \implies B(0, 7.5) \implies OB = 7.5\] - At point \(A\) on the \(x\)-axis, \(y = 0\): \[0 = -\frac{1}{2}x + 7.5 \implies \frac{1}{2}x = 7.5 \implies x = 15 \implies A(15, 0) \implies OA = 15\]
5. Calculate the area of triangle \(OAB\): \[\text{Area} = \frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times 15 \times 7.5 = 56.25\]
Marking scheme
M1 for finding gradient of radius \(OP = \frac{6}{3} = 2\) M1 for gradient of tangent \(= -\frac{1}{\text{their } 2} = -\frac{1}{2}\) M1 for finding the equation of the tangent or finding both coordinates \(A(15, 0)\) and \(B(0, 7.5)\) M1 for \(\frac{1}{2} \times \text{their } 15 \times \text{their } 7.5\) oe A1 for \(56.25\) or \(\frac{225}{4}\) or \(56\frac{1}{4}\) with correct working shown
Question 5 · free-response
6 marks
\(P\) is a port, \(L\) is a lighthouse and \(B\) is a buoy.
- \(L\) is on a bearing of \(035^\circ\) from \(P\). - The distance from \(P\) to \(L\) is \(14\text{ km}\). - \(B\) is on a bearing of \(080^\circ\) from \(P\). - \(B\) is on a bearing of \(115^\circ\) from \(L\).
Calculate the direct distance from \(P\) to \(B\). Give your answer to 3 significant figures. You must show your working.
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2. Find angle \(\angle PLB\): The back-bearing from \(L\) to \(P\) is: \[35^\circ + 180^\circ = 215^\circ\] The bearing of \(B\) from \(L\) is \(115^\circ\). Therefore, the interior angle at \(L\) is: \[\angle PLB = 215^\circ - 115^\circ = 100^\circ\]
4. Use the sine rule in triangle \(PLB\) to find \(PB\): \[\frac{PB}{\sin(100^\circ)} = \frac{14}{\sin(35^\circ)}\] \[PB = \frac{14 \times \sin(100^\circ)}{\sin(35^\circ)}\] \[PB = \frac{14 \times 0.9848077...}{0.5735764...} \approx 24.0378...\text{ km}\]
To 3 significant figures, \(PB = 24.0\text{ km}\).
Marking scheme
B1 for angle \(\angle LPB = 45^\circ\) M1 for a correct method to find angle \(\angle PLB\), e.g. \(180 + 35 - 115\) or \(180 - (180 - 115 + 35)\) A1 for \(\angle PLB = 100^\circ\) B1 for \(\angle PBL = 35^\circ\) (or \(180 - 100 - 45\)) M1 for \(\frac{PB}{\sin(\text{their } 100^\circ)} = \frac{14}{\sin(\text{their } 35^\circ)}\) oe A1 for answer in the range \(24.0\) to \(24.04\) with correct working shown
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