An original Thinka practice paper modelled on the structure and difficulty of the Nov 2025 (V3) Cambridge IGCSE International Mathematics (0607) paper. Not affiliated with or reproduced from Cambridge.
Paper 23 Non-calculator Extended
Answer all questions. Calculators must not be used. Show all necessary working clearly.
17 Question · 58.48000000000001 marks
Question 1 · Short Answer
3.53 marks
These are the first four terms of a sequence.
\(17, \quad 13, \quad 9, \quad 5\)
Find the \(n\)th term of this sequence.
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Worked solution
The sequence starts at 17 and decreases by 4 each time. This is an arithmetic sequence with first term \(a = 17\) and common difference \(d = -4\). The formula for the \(n\)th term is: \(17 + (n-1)(-4) = 17 - 4n + 4 = 21 - 4n\).
Marking scheme
M1 for \(-4n + c\) or \(kn + 21\) (where \(k \neq 0\)) A1 for \(21 - 4n\) or \(-4n + 21\)
Question 2 · Short Answer
3.53 marks
Liam buys 5 notebooks and 3 pens. Each notebook costs $1.20 and each pen costs $0.85. He pays with a $10 bill. Work out the change he receives.
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Worked solution
1. Calculate the cost of 5 notebooks: \(5 \times \$1.20 = \$6.00\)
2. Calculate the cost of 3 pens: \(3 \times \$0.85 = \$2.55\)
3. Calculate the total cost: \(\$6.00 + \$2.55 = \$8.55\)
4. Calculate the change received from a $10 bill: \(\$10.00 - \$8.55 = \$1.45\).
Marking scheme
M1 for showing the total cost is $8.55 M1 for subtracting their total cost from $10.00 A1 for 1.45
Question 3 · Short Answer
3.53 marks
Let \(f(x) = 3x - 7\). Find the value of \(x\) when \(f(x) = 11\).
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Worked solution
Set the function equal to 11: \(3x - 7 = 11\) Add 7 to both sides: \(3x = 18\) Divide by 3: \(x = 6\).
Marking scheme
M1 for setting up the equation \(3x - 7 = 11\) M1 for solving to find \(3x = 18\) A1 for 6
Question 4 · Short Answer
3.53 marks
Simplify.
\(4a - 3b - 2a + 7b\)
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Worked solution
Group the like terms together: \((4a - 2a) + (-3b + 7b)\) Simplify each group: \(2a + 4b\).
Marking scheme
M1 for identifying and combining like terms, showing either \(2a\) or \(4b\) correct in the final expression A1 for \(2a + 4b\) or \(4b + 2a\)
Question 5 · Short Answer
3.53 marks
The \(n\)th term of a sequence is \(n^2 - 3\). Find the first three terms of this sequence.
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Worked solution
Find the terms by substituting \(n = 1, 2, 3\):
- First term (\(n=1\)): \(1^2 - 3 = 1 - 3 = -2\) - Second term (\(n=2\)): \(2^2 - 3 = 4 - 3 = 1\) - Third term (\(n=3\)): \(3^2 - 3 = 9 - 3 = 6\)
The first three terms are \(-2, 1, 6\).
Marking scheme
M1 for substituting \(n=1, 2, 3\) to find at least two terms correctly A1 for \(-2, 1, 6\) (must be in the correct order)
Question 6 · Short Answer
3.53 marks
The exchange rate between dollars ($) and euros (€) is \(\$1 = €0.90\). Convert €540 into dollars.
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Worked solution
To convert from euros to dollars, divide the amount in euros by 0.90:
M1 for writing down or showing the operation \(540 \div 0.90\) A1 for 600
Question 7 · Short Answer
3.53 marks
Let \(g(x) = \frac{12}{x+1}\). Find the value of \(g(3)\).
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Worked solution
Substitute \(x = 3\) into the expression:
\(g(3) = \frac{12}{3+1} = \frac{12}{4} = 3\).
Marking scheme
M1 for substituting \(x = 3\) correctly to get \(\frac{12}{3+1}\) A1 for 3
Question 8 · Short Answer
3.53 marks
Factorise fully.
\(12x^2 - 8x\)
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Worked solution
1. Find the highest common factor (HCF) of the numerical coefficients 12 and 8, which is 4. 2. Find the HCF of the variables \(x^2\) and \(x\), which is \(x\). 3. The common factor to pull out is \(4x\):
\(12x^2 - 8x = 4x(3x - 2)\).
Marking scheme
M1 for identifying a partial common factor, e.g., \(4(3x^2 - 2x)\) or \(x(12x - 8)\) or \(2x(6x - 4)\) A1 for \(4x(3x - 2)\)
Question 9 · Short Answer
3.53 marks
Pierre exchanges 300 Euros (€) into Dollars ($) when the exchange rate is €1 = $1.15. Calculate the amount of Dollars Pierre receives.
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Worked solution
Pierre receives: \(300 \times 1.15 = 345\) dollars.
Marking scheme
M1 for \(300 \times 1.15\) or equivalent, A1 for 345.
Question 10 · Short Answer
3.53 marks
These are the first four terms of a sequence: 7, 11, 15, 19. Find the \(n\)th term of this sequence.
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Worked solution
The sequence is arithmetic with a common difference of 4. The first term is 7. Thus, the \(n\)th term is: \(7 + (n-1) \times 4 = 4n + 3\).
Marking scheme
B1 for \(4n + c\) (where \(c \neq 3\)) or \(kn + 3\) (where \(kn \neq 4\)), B1 for \(4n + 3\).
Question 11 · Short Answer
3.53 marks
Given \(f(x) = 5 - 3x\). Find the value of \(f(-4)\).
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Worked solution
Substitute \(x = -4\) into the function: \(f(-4) = 5 - 3(-4) = 5 + 12 = 17\).
Marking scheme
M1 for substituting \(-4\) into the expression correctly, A1 for 17.
Question 12 · Short Answer
3.53 marks
Factorise completely: \(12a^2b - 18ab^2\)
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Worked solution
The highest common factor of \(12a^2b\) and \(18ab^2\) is \(6ab\). Factorising this out gives: \(6ab(2a - 3b)\).
Marking scheme
B1 for finding a partial common factor such as \(3ab\) or \(6a\), B1 for fully factorised correct expression.
Question 13 · Short Answer
3.53 marks
Work out the value of \(5^2 \times 2^3 - 3^2\).
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Worked solution
Calculate the powers first: \(5^2 = 25\), \(2^3 = 8\), \(3^2 = 9\). Then multiply and subtract: \(25 \times 8 - 9 = 200 - 9 = 191\).
Marking scheme
M1 for evaluating at least two powers correctly, M1 for \(200 - 9\), A1 for 191.
Question 14 · Short Answer
3.53 marks
Write \(0.00045\) in standard form.
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Worked solution
To express \(0.00045\) in standard form, move the decimal point 4 places to the right to get \(4.5\), which gives: \(4.5 \times 10^{-4}\).
Marking scheme
B1 for \(4.5 \times 10^k\) (where \(k \neq -4\)) or \(c \times 10^{-4}\) (where \(c \neq 4.5\)), B1 for the correct standard form.
Question 15 · Short Answer
3.53 marks
Solve the equation: \(3(2x - 5) = 21\)
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Worked solution
Divide both sides by 3: \(2x - 5 = 7\). Add 5 to both sides: \(2x = 12\). Divide by 2: \(x = 6\).
Marking scheme
M1 for expanding the bracket to \(6x - 15 = 21\) or dividing both sides by 3 to get \(2x - 5 = 7\), M1 for isolating the \(x\) term, A1 for 6.
Question 16 · Short Answer
3.53 marks
A rectangle has a perimeter of 32 cm. The width of the rectangle is 6 cm. Find the area of the rectangle.
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Worked solution
The perimeter formula is \(2 \times (\text{length} + \text{width}) = 32\). Thus, \(\text{length} + 6 = 16\), so \(\text{length} = 10\) cm. The area is \(\text{length} \times \text{width} = 10 \times 6 = 60\text{ cm}^2\).
Marking scheme
M1 for using the perimeter formula to find the length, A1 for length = 10, M1 for calculating area using their length, A1 for 60.
Question 17 · Short Answer
2 marks
The points \(P\) and \(Q\) have coordinates \((-4, 7)\) and \((6, -1)\) respectively. Calculate the coordinates of the midpoint of the line segment \(PQ\).
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Worked solution
To find the midpoint of \(PQ\), calculate the average of the \(x\)-coordinates and the average of the \(y\)-coordinates. For \(x\): \(\frac{-4 + 6}{2} = 1\). For \(y\): \(\frac{7 + (-1)}{2} = 3\). Therefore, the coordinates of the midpoint are \((1, 3)\).
Marking scheme
M1 for showing a correct method for at least one coordinate, e.g. \(\frac{-4+6}{2}\) or \(\frac{7-1}{2}\). A1 for \((1, 3)\).
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21 Question · 74.96999999999997 marks
Question 1 · Short Answer
3.57 marks
A shopkeeper buys a bicycle for 160 Euros. She sells it in her shop for 270 US Dollars ($). The exchange rate is 1 Euro = 1.25 $. Calculate her percentage profit.
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Worked solution
First, convert the selling price from USD ($) to Euros: \(270 \div 1.25 = 270 \div \frac{5}{4} = 270 \times \frac{4}{5} = 54 \times 4 = 216\) Euros. Next, calculate the profit in Euros: \(216 - 160 = 56\) Euros. Finally, find the percentage profit: \(\frac{56}{160} \times 100 = \frac{7}{20} \times 100 = 35\%\).
Marking scheme
M1 for converting selling price to Euros (216) or cost price to USD (200). M1 for calculating profit (56 Euros or 70 USD). A1 for 35.
Question 2 · Short Answer
3.57 marks
Let \(f(x) = \frac{3}{2x - 1}\) for \(x \neq \frac{1}{2}\) and \(g(x) = 2x + 3\). Find the value of \(x\) when \(g(f(x)) = 5\).
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Worked solution
Substitute \(f(x)\) into \(g(x)\): \(g(f(x)) = 2\left(\frac{3}{2x - 1}\right) + 3 = \frac{6}{2x - 1} + 3\). Set the expression equal to 5: \(\frac{6}{2x - 1} + 3 = 5 \implies \frac{6}{2x - 1} = 2\). Solve for \(x\): \(2x - 1 = 3 \implies 2x = 4 \implies x = 2\).
Marking scheme
M1 for writing the composite function g(f(x)) as \(\frac{6}{2x-1} + 3\). M1 for setting their expression equal to 5 and solving the linear equation. A1 for 2.
Question 3 · Short Answer
3.57 marks
Factorise fully: \(6a^2 - 15ab - 4ac + 10bc\).
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Worked solution
Group the terms to find common factors: \((6a^2 - 15ab) - (4ac - 10bc)\). Factor out \(3a\) from the first group and \(2c\) from the second group: \(3a(2a - 5b) - 2c(2a - 5b)\). Factor out the common binomial term \((2a - 5b)\): \((3a - 2c)(2a - 5b)\).
Marking scheme
M1 for grouping and factorising two terms correctly, e.g., \(3a(2a-5b)\) or \(-2c(2a-5b)\). A1 for \((3a - 2c)(2a - 5b)\) or equivalent.
Question 4 · Short Answer
3.57 marks
These are the first five terms of a sequence: 3, 9, 17, 27, 39. Find the \(n\)th term of this sequence.
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Worked solution
Find the first differences: 6, 8, 10, 12. Find the second differences: 2, 2, 2. Since the second difference is constant, the sequence is quadratic with an \(n^2\) term of coefficient \(\frac{2}{2} = 1\). Subtracting \(n^2\) from each term gives: \(3 - 1^2 = 2\), \(9 - 2^2 = 5\), \(17 - 3^2 = 8\), \(27 - 4^2 = 11\). The resulting linear sequence is 2, 5, 8, 11, which has the formula \(3n - 1\). Combining these, the \(n\)th term is \(n^2 + 3n - 1\).
Marking scheme
M1 for finding second difference of 2. M1 for subtracting \(n^2\) from terms to find the linear sequence 2, 5, 8, 11... or equivalent method. A1 for \(n^2 + 3n - 1\).
Question 5 · Short Answer
3.57 marks
Solve the equation: \(9^{x+1} \times 3^{x-2} = \frac{1}{27}\).
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Worked solution
Express all terms with a base of 3: \(9^{x+1} = (3^2)^{x+1} = 3^{2x+2}\) and \(\frac{1}{27} = 3^{-3}\). Substitute these into the equation: \(3^{2x+2} \times 3^{x-2} = 3^{-3}\). Simplify using index laws: \(3^{(2x+2) + (x-2)} = 3^{-3} \implies 3^{3x} = 3^{-3}\). Equate the exponents: \(3x = -3 \implies x = -1\).
Marking scheme
M1 for expressing 9 and 27 as powers of 3. M1 for applying index laws correctly to get \(3^{3x} = 3^{-3}\). A1 for -1.
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Worked solution
First, rationalise the denominator of the fraction: \(\frac{4}{\sqrt{5} - 1} \times \frac{\sqrt{5} + 1}{\sqrt{5} + 1} = \frac{4(\sqrt{5} + 1)}{5 - 1} = \frac{4(\sqrt{5} + 1)}{4} = \sqrt{5} + 1\). Now substitute this back into the original expression: \((\sqrt{5} + 1) - \sqrt{5} = 1\).
Marking scheme
M1 for multiplying the numerator and denominator by the conjugate \(\sqrt{5}+1\). M1 for simplifying to \(\sqrt{5}+1\). A1 for 1.
Question 7 · Short Answer
3.57 marks
A, B, C and D are points on a circle. The diagonals AC and BD intersect at X. Angle ABD = 38° and angle AXB = 100°. Find the size of angle BDC.
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Worked solution
In triangle ABX, the sum of angles is 180°: \(\text{Angle BAX} = 180° - 100° - 38° = 42°\). Angle BAC (which is the same as angle BAX) and angle BDC are subtended by the same arc BC. Therefore, by circle theorems, \(\text{Angle BDC} = \text{Angle BAC} = 42°\).
Marking scheme
M1 for finding angle BAX = 180° - (100° + 38°). M1 for identifying that angle BDC = angle BAX (angles in same segment). A1 for 42.
Question 8 · Short Answer
3.57 marks
A bag contains 5 red beads and 3 blue beads. Two beads are selected at random without replacement. Find the probability that the two beads are of different colours.
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Worked solution
The total number of beads is 8. The probability of picking different colours is the probability of picking Red then Blue, plus the probability of picking Blue then Red. \(P(\text{Red, Blue}) = \frac{5}{8} \times \frac{3}{7} = \frac{15}{56}\). \(P(\text{Blue, Red}) = \frac{3}{8} \times \frac{5}{7} = \frac{15}{56}\). Total probability = \frac{15}{56} + \frac{15}{56} = \frac{30}{56} = \frac{15}{28}.
Marking scheme
M1 for identifying the two scenarios (Red then Blue, and Blue then Red). M1 for calculating one correct product of probabilities without replacement, e.g., \(\frac{5}{8} \times \frac{3}{7}\). A1 for \(\frac{15}{28}\) or equivalent fraction.
Question 9 · Short Answer
3.57 marks
A traveler exchanges 600 Euros (EUR) into Singapore Dollars (SGD) when the exchange rate is \(1\text{ EUR} = 1.45\text{ SGD}\). Later, they exchange all the SGD back into Euros when the exchange rate is \(1\text{ EUR} = 1.50\text{ SGD}\). Calculate the overall loss in Euros.
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Worked solution
1. Convert Euros to SGD: \(600 \times 1.45 = 870\text{ SGD}\). 2. Convert SGD back to Euros: \(870 \div 1.50 = 580\text{ Euros}\). 3. Calculate the loss: \(600 - 580 = 20\text{ Euros}\).
Marking scheme
M1 for \(600 \times 1.45\) M1 for their \(870 \div 1.50\) A1 for 20
Question 10 · Short Answer
3.57 marks
Let \(f(x) = 3x - 2\) and \(g(x) = \frac{x+1}{2}\). Find the value of \(x\) when \(f(g(x)) = g^{-1}(x)\).
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M1 for finding \(g^{-1}(x) = 2x-1\) M1 for setting up the equation \(\frac{3x-1}{2} = 2x-1\) A1 for 1
Question 11 · Short Answer
3.57 marks
Rearrange the formula to make \(v\) the subject: \(u = \frac{v+3}{2v-1}\).
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Worked solution
Multiply both sides by \(2v-1\): \(u(2v-1) = v+3 \implies 2uv - u = v+3\). Rearrange to group terms with \(v\) on one side: \(2uv - v = u+3\). Factorise \(v\): \(v(2u-1) = u+3\). Divide by \(2u-1\): \(v = \frac{u+3}{2u-1}\).
Marking scheme
M1 for multiplying by \(2v-1\) M1 for grouping terms in \(v\) on one side A1 for \(\frac{u+3}{2u-1}\)
Question 12 · Short Answer
3.57 marks
These are the first four terms of a sequence: \[\frac{3}{5}, \frac{7}{10}, \frac{11}{17}, \frac{15}{26}, \dots\] Find the 10th term of this sequence.
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Worked solution
The numerators are \(3, 7, 11, 15, \dots\) which is an arithmetic sequence with \(n\)-th term \(4n - 1\). For \(n = 10\), the numerator is \(4(10) - 1 = 39\). The denominators are \(5, 10, 17, 26, \dots\) which can be represented by \((n+1)^2 + 1\). For \(n = 10\), the denominator is \((10+1)^2 + 1 = 121 + 1 = 122\). Thus, the 10th term is \(\frac{39}{122}\).
Marking scheme
M1 for identifying the 10th numerator is 39 M1 for identifying the 10th denominator is 122 A1 for \(\frac{39}{122}\)
Question 13 · Short Answer
3.57 marks
Emma invests \(\$4000\) in an account paying \(3\%\) per year compound interest. At the end of \(2\) years, she withdraws the entire amount and spends \(15\%\) of it on a new computer. Calculate the amount of money she has left.
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Worked solution
The value of the investment at the end of 2 years is: \(4000 \times (1.03)^2 = 4000 \times 1.0609 = \$4243.60\). She spends \(15\%\) on a computer, leaving \(85\%\) of the money: \(4243.60 \times 0.85 = \$3607.06\).
Marking scheme
M1 for \(4000 \times (1.03)^2\) M1 for their \(4243.60 \times 0.85\) A1 for 3607.06
Question 14 · Short Answer
3.57 marks
The function \(f(x) = a \cdot 2^{-x} + b\) has a horizontal asymptote at \(y = 3\) and passes through the point \((0, 8)\). Find the value of \(f(-1)\).
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Worked solution
As \(x \to \infty\), \(2^{-x} \to 0\), so \(f(x) \to b\). Given the horizontal asymptote is \(y = 3\), we have \(b = 3\). Since the graph passes through \((0, 8)\): \(f(0) = a \cdot 2^0 + b = a + 3 = 8 \implies a = 5\). Thus, the function is \(f(x) = 5 \cdot 2^{-x} + 3\). Evaluating at \(x = -1\): \(f(-1) = 5 \cdot 2^1 + 3 = 10 + 3 = 13\).
Marking scheme
B1 for identifying \(b = 3\) M1 for finding \(a = 5\) A1 for 13
Question 15 · Short Answer
3.57 marks
Find the larger value of \(x\) that satisfies the equation \(\frac{8}{x+2} - \frac{1}{x-1} = 1\).
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Worked solution
Multiply the entire equation by \((x+2)(x-1)\): \(8(x-1) - (x+2) = (x+2)(x-1)\) \(8x - 8 - x - 2 = x^2 + x - 2\) \(7x - 10 = x^2 + x - 2\) \(x^2 - 6x + 8 = 0\) \((x-2)(x-4) = 0\) The solutions are \(x = 2\) and \(x = 4\). The larger value of \(x\) is 4.
Marking scheme
M1 for eliminating the denominators M1 for the quadratic equation \(x^2 - 6x + 8 = 0\) A1 for 4
Question 16 · Short Answer
3.57 marks
The \(n\)-th term of a sequence is \(u_n = an^2 + bn\). The second term of the sequence is 14 and the fifth term is 65. Find the tenth term of this sequence.
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Worked solution
From the given terms, set up simultaneous equations: For \(n = 2\): \(a(2)^2 + b(2) = 14 \implies 4a + 2b = 14 \implies 2a + b = 7\). For \(n = 5\): \(a(5)^2 + b(5) = 65 \implies 25a + 5b = 65 \implies 5a + b = 13\). Subtracting the first equation from the second: \(3a = 6 \implies a = 2\). Substituting \(a = 2\) into the first equation: \(2(2) + b = 7 \implies b = 3\). Thus, the general term is \(u_n = 2n^2 + 3n\). Evaluating for the tenth term (\(n = 10\)): \(u_{10} = 2(10)^2 + 3(10) = 200 + 30 = 230\).
Marking scheme
M1 for setting up simultaneous equations M1 for finding both \(a = 2\) and \(b = 3\) A1 for 230
Question 17 · Short Answer
3.57 marks
Amara invests a principal sum of \(P\) dollars in a savings account at a simple interest rate of \(5\%\) per year. At the end of 4 years, the total value of her investment is \(\$1440\). Calculate the value of \(P\).
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Worked solution
We use the simple interest formula for the total amount \(A\): \(A = P(1 + rt)\) where \(r = 0.05\) (rate of interest as a decimal) and \(t = 4\) (time in years).
Substitute the given values into the formula: \(1440 = P(1 + 0.05 \times 4)\) \(1440 = P(1 + 0.20)\) \(1440 = 1.2P\)
Solve for \(P\): \(P = \frac{1440}{1.2} = \frac{14400}{12} = 1200\)
Marking scheme
M1 for setting up the equation \(P(1 + 0.05 \times 4) = 1440\) or equivalent. M1 for simplifying to \(1.2P = 1440\) or \(P = \frac{1440}{1.2}\). A1.57 for the correct final answer 1200.
Question 18 · Short Answer
3.57 marks
The function \(\mathrm{f}(x)\) is defined as \(\mathrm{f}(x) = \frac{5x - 2}{2x + 3}\) for \(x \neq -1.5\). Find \(\mathrm{f}^{-1}(x)\).
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Worked solution
To find the inverse function, let \(y = \mathrm{f}(x)\): \(y = \frac{5x - 2}{2x + 3}\)
Multiply both sides by \((2x + 3)\) to clear the fraction: \(y(2x + 3) = 5x - 2\) \(2xy + 3y = 5x - 2\)
Rearrange the terms to group all \(x\) terms on one side: \(2xy - 5x = -3y - 2\)
Factorise \(x\) from the left-hand side: \(x(2y - 5) = -(3y + 2)\)
Divide by \((2y - 5)\): \(x = \frac{-(3y + 2)}{2y - 5} = \frac{3y + 2}{5 - 2y} Replace \)y\) with \(x\) to get the inverse function: \(\mathrm{f}^{-1}(x) = \frac{3x + 2}{5 - 2x}\)
Marking scheme
M1 for setting up \(y = \frac{5x - 2}{2x + 3}\) and rearranging to clear the fraction: \(y(2x + 3) = 5x - 2\). M1 for collecting terms in \(x\) and factorising: \(x(2y - 5) = -3y - 2\) or equivalent. A1.57 for final answer \(\frac{3x + 2}{5 - 2x}\) (or equivalent form).
Question 19 · Short Answer
3.57 marks
Write as a single fraction in its simplest form. \(\frac{4}{x-2} - \frac{3}{2x+1}\)
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Worked solution
To subtract the fractions, find a common denominator, which is \((x - 2)(2x + 1)\): \(\frac{4}{x-2} - \frac{3}{2x+1} = \frac{4(2x + 1) - 3(x - 2)}{(x - 2)(2x + 1)} Expand the numerator: \)4(2x + 1) - 3(x - 2) = 8x + 4 - 3x + 6\)
Simplify the numerator by collecting like terms: \(8x - 3x + 4 + 6 = 5x + 10\)
Thus, the single fraction is: \(\frac{5x + 10}{(x - 2)(2x + 1)}\)
We can also factorise the numerator: \(\frac{5(x + 2)}{(x - 2)(2x + 1)}\)
Marking scheme
M1 for placing over a common denominator: \(\frac{4(2x + 1) - 3(x - 2)}{(x - 2)(2x + 1)}\). M1 for expanding the numerator correctly to obtain \(8x + 4 - 3x + 6\). A1.57 for the correct simplified fraction \(\frac{5x + 10}{(x - 2)(2x + 1)}\) or \(\frac{5(x + 2)}{(x - 2)(2x + 1)}\).
Question 20 · Short Answer
3.57 marks
These are the first four terms of a sequence. \(3, \quad 8, \quad 15, \quad 24\) Find the \(n\)-th term of this sequence.
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Worked solution
Let us look at the differences between successive terms of the sequence: First differences: \(8-3 = 5\), \(15-8 = 7\), \(24-15 = 9\). Second differences: \(7-5 = 2\), \(9-7 = 2\).
Since the second differences are constant, the sequence is quadratic of the form \(an^2 + bn + c\). The coefficient of \(n^2\) is half of the second difference: \(a = \frac{2}{2} = 1\) So the term contains \(n^2\).
Let us subtract \(n^2\) from each term in the sequence: For \(n = 1\): \(3 - 1^2 = 2\) For \(n = 2\): \(8 - 2^2 = 4\) For \(n = 3\): \(15 - 3^2 = 6\) For \(n = 4\): \(24 - 4^2 = 8\)
The resulting linear sequence is \(2, 4, 6, 8, \dots\), which has the \(n\)-th term \(2n\).
Therefore, the \(n\)-th term of the original sequence is: \(n^2 + 2n\)
Marking scheme
M1 for finding first and second differences to establish a quadratic relation with an \(n^2\) term. M1 for establishing the linear component \(2n\). A1.57 for the final answer \(n^2 + 2n\) or \(n(n+2)\).
Question 21 · Short Answer
3.57 marks
Solve the equation. \(4^{2x + 1} = 32^{x - 3}\)
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Worked solution
Express both bases, 4 and 32, as powers of 2: \(4 = 2^2\) \(32 = 2^5\)
Substitute these into the equation: \((2^2)^{2x + 1} = (2^5)^{x - 3}\)
Apply the power of a power rule \((a^m)^n = a^{mn}\): \(2^{2(2x + 1)} = 2^{5(x - 3)}\) \(2^{4x + 2} = 2^{5x - 15}\)
Since the bases are the same, equate the exponents: \(4x + 2 = 5x - 15\)
M1 for expressing both sides as powers of 2: \((2^2)^{2x + 1} = (2^5)^{x - 3}\). M1 for equating the exponents: \(2(2x + 1) = 5(x - 3)\) or \(4x + 2 = 5x - 15\). A1.57 for final answer 17 or \(x = 17\).
Paper 63 Investigation and Modelling Extended
Answer both Section A (Investigation) and Section B (Modelling). Provide full communication and steps.
18 Question · 54 marks
Question 1 · Short Answer
3 marks
Elena invests $4500 in a savings account. The account pays 3.2% per year simple interest. Calculate the total value of her investment at the end of 6 years.
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Worked solution
Elena's interest earned over 6 years is calculated using the formula: \(\text{Interest} = \frac{P \times R \times T}{100}\). Substituting the values: \(\text{Interest} = \frac{4500 \times 3.2 \times 6}{100} = 864\). The total value is the principal plus interest: \(4500 + 864 = 5364\).
Marking scheme
M1 for interest calculation: \(4500 \times 0.032 \times 6\) (or 864) M1 for adding the interest to the principal: \(4500 + \text{their interest}\) A1 for 5364
Question 2 · Short Answer
3 marks
Let \(f(x) = 3x^2 - 5x + 2\). Find the value of \(f(-3)\).
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M1 for expanding to get at least three correct terms out of \(2x^2, 10x, -3x, -15\) A1 for simplifying the linear terms to \(7x\) A1 for the correct final trinomial \(2x^2 + 7x - 15\)
Question 4 · Short Answer
3 marks
These are the first four terms of a sequence: 4, 11, 18, 25, ... Find the \(n\)-th term of this sequence.
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Worked solution
The difference between consecutive terms is \(11 - 4 = 7\), which indicates a linear sequence of the form \(7n + c\). Using the first term where \(n = 1\): \(7(1) + c = 4 \implies c = -3\). Therefore, the \(n\)-th term is \(7n - 3\).
Marking scheme
M1 for finding the common difference of 7 M1 for the term of the form \(7n + k\) where \(k\) is any constant A1 for \(7n - 3\)
Question 5 · Short Answer
3 marks
A laptop originally costs $850. In a sale, the price is reduced by 15%. Calculate the sale price of the laptop.
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Worked solution
The reduced price can be found by calculating 85% of the original price: \(850 \times (1 - 0.15) = 850 \times 0.85 = 722.50\).
Marking scheme
M1 for finding the reduction: \(850 \times 0.15 = 127.50\) or for using the multiplier \(0.85\) M1 for subtracting the reduction from the original price: \(850 - 127.50\) A1 for 722.50 (accept 722.5)
Question 6 · Short Answer
3 marks
The function \(y = 4^x - 3\) is defined for all real values of \(x\). Find the value of \(y\) when \(x = 2.5\). Give your answer as a decimal.
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Worked solution
Substitute \(x = 2.5\) into the equation: \(y = 4^{2.5} - 3\). Since \(4^{2.5} = (4^{1/2})^5 = 2^5 = 32\), we have \(y = 32 - 3 = 29\).
Marking scheme
M1 for correct substitution of \(x = 2.5\) into the function M1 for evaluating \(4^{2.5} = 32\) A1 for 29
Question 7 · Short Answer
3 marks
Solve the equation: \(\frac{3x - 1}{4} = 5\)
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Worked solution
Multiply both sides of the equation by 4: \(3x - 1 = 20\). Add 1 to both sides: \(3x = 21\). Divide both sides by 3: \(x = 7\).
Marking scheme
M1 for isolating the numerator: \(3x - 1 = 20\) M1 for isolating the term with \(x\): \(3x = 21\) A1 for 7
Question 8 · Short Answer
3 marks
The \(n\)-th term of a sequence is \(3n^2 - 2\). Find the 5th term of this sequence.
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Worked solution
To find the 5th term, substitute \(n = 5\) into the \(n\)-th term formula: \(3(5^2) - 2 = 3(25) - 2 = 75 - 2 = 73\).
Marking scheme
M1 for substituting \(n = 5\) into the expression: \(3(5)^2 - 2\) A1 for evaluating the power and multiplication: \(75 - 2\) A1 for 73
Question 9 · Short Answer
3 marks
Evelyn invests $4200 at a rate of 3.25% per year simple interest. Calculate the total value of her investment at the end of 6 years.
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Worked solution
Simple Interest = \( \frac{P \times R \times T}{100} = \frac{4200 \times 3.25 \times 6}{100} = 819 \). Total value = \( 4200 + 819 = 5019 \).
Marking scheme
M1 for \( \frac{4200 \times 3.25 \times 6}{100} \), A1 for 819 (interest), A1 for 5019 (total value)
Question 10 · Short Answer
3 marks
A store buys a jacket for $75 and sells it for $108. Calculate the percentage profit.
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M1 for evaluating \(f(4) = 7\), M1 for evaluating \(g(3) = 19\), A1 for 26
Question 12 · Short Answer
3 marks
Let \(f(x) = 5x - 12\). Find the value of \(x\) when \(f(x) = 18\).
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Worked solution
Set the function equal to 18: \(5x - 12 = 18 \Rightarrow 5x = 30 \Rightarrow x = 6\).
Marking scheme
M1 for setting up \(5x - 12 = 18\), M1 for rearranging to \(5x = 30\), A1 for 6
Question 13 · Short Answer
3 marks
Expand and simplify \(3(2x - 5) - 2(x - 4)\).
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Worked solution
Expanding the brackets gives \(6x - 15 - 2x + 8\). Combining like terms yields \(4x - 7\).
Marking scheme
M1 for \(6x - 15\), M1 for \(-2x + 8\), A1 for \(4x - 7\)
Question 14 · Short Answer
3 marks
Factorise fully \(12x^2y - 18xy^2\).
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Worked solution
The highest common factor of 12 and 18 is 6. The highest common factor of \(x^2y\) and \(xy^2\) is \(xy\). Factoring out \(6xy\) gives \(6xy(2x - 3y)\).
Marking scheme
M1 for identifying a common factor of at least \(6\), \(x\), or \(y\), A1 for the correct terms inside bracket \((2x - 3y)\), A1 for the fully factorised expression \(6xy(2x - 3y)\)
Question 15 · Short Answer
3 marks
These are the first four terms of a sequence: 8, 15, 22, 29. Find the nth term of the sequence.
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Worked solution
The sequence has a constant difference of 7. The general term is of the form \(7n + c\). Since the first term is 8, \(7(1) + c = 8 \Rightarrow c = 1\). Therefore, the nth term is \(7n + 1\).
Marking scheme
M1 for finding the common difference of 7, M1 for setting up \(7n + c\), A1 for \(7n + 1\)
Question 16 · Short Answer
3 marks
A sequence has first term 5. The rule to find the next term is 'multiply the previous term by 2 and subtract 3'. Find the 4th term of this sequence.
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Worked solution
Term 1 = 5. Term 2 = \(5 \times 2 - 3 = 7\). Term 3 = \(7 \times 2 - 3 = 11\). Term 4 = \(11 \times 2 - 3 = 19\).
Marking scheme
M1 for finding Term 2 = 7, M1 for finding Term 3 = 11, A1 for Term 4 = 19
Question 17 · Short/Medium Answer
3 marks
Elena invests $6500 at a rate of 2.3% per year compound interest. Calculate the total interest earned on this investment at the end of 4 years. Give your answer correct to the nearest cent.
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Worked solution
To find the total value of the investment, \(A\), after 4 years, use the compound interest formula: \(A = P\left(1 + \frac{r}{100}\right)^t\). Substituting the given values: \(A = 6500(1.023)^4 \approx 7118.949169\). Subtracting the principal to find the interest earned: \(\text{Interest} = 7118.949169 - 6500 = 618.949169\). Rounding to the nearest cent gives \(618.95\).
Marking scheme
M1 for \(6500 \times (1.023)^4\) oe. A1 for \(7118.95\) (or \(7118.949...\)). A1 for \(618.95\).
Question 18 · Short/Medium Answer
3 marks
The \(n\)th term of a sequence is \(2n^2 - 5\). Work out the first three terms of this sequence.
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Worked solution
To find the first three terms, substitute \(n = 1\), \(n = 2\), and \(n = 3\) into the expression \(2n^2 - 5\): For \(n = 1\): \(2(1)^2 - 5 = -3\). For \(n = 2\): \(2(2)^2 - 5 = 3\). For \(n = 3\): \(2(3)^2 - 5 = 13\). The first three terms are \(-3, 3, 13\).
Marking scheme
B1 for each correct term: \(-3\), \(3\), and \(13\).
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