Direct and Inverse Proportion: Edexcel 4MA1 Past Paper Questions and Worked Solutions
This page collects every direct and inverse proportion question from the Pearson Edexcel International GCSE Mathematics A (4MA1) Higher tier Paper 1H and Paper 1HR, January 2020 to June 2025: 7 questions worth 28 marks. Questions run from easier to harder. Try each one first, then click “Show solution” for a step-by-step method with the reason for every step. All answers are checked against the official Pearson mark schemes.
F is inversely proportional to the square of v. Given that F = 6.5 when v = 4, find a formula for F in terms of v.
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- “Inversely proportional to the square of v” means F = kv2
- Substitute F = 6.5 and v = 4: 6.5 = k16
- Multiply both sides by 16: k = 104
Answer: F = 104v2
A is inversely proportional to C2. A = 40 when C = 1.5. Calculate the value of C when A = 1000.
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- A = kC2: 40 = k2.25, so k = 90
- 1000 = 90C2, so C2 = 0.09
Answer: C = 0.3
y is inversely proportional to √x. y = c4 when x = c2 where c is a positive constant. Find a formula for y in terms of x and c. Give your answer in its simplest form.
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- y = k√x
- Substitute: c4 = k√c2 = kc, so k = c5
Answer: y = c5√x
F is inversely proportional to the square of r. F = 36 when r = 4.
(a) Find a formula for F in terms of r. (3)
(b) Work out the value of F when r = 48. (1)
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Part (a)
- F = kr2
- Substitute: 36 = k16, so k = 36 × 16 = 576
Answer: F = 576r2
Part (b)
- F = 576482 = 5762304
Answer: 0.25
y is inversely proportional to x3. y = 4 when x = 3. Work out the value of x when y = 864.
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- Inversely proportional to x3 means y = kx3 for some constant k.
- Use y = 4 when x = 3: 4 = k27, so k = 108 and y = 108x3
- Substitute y = 864: 864 = 108x3, so x3 = 108 ÷ 864 = 0.125
- x = ∛0.125
Answer: x = 0.5
F is inversely proportional to the cube of r. F = 6 when r = 2.
(a) Find a formula for F in terms of r. (3)
(b) Find the value of r when F = 3072. (2)
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Part (a)
- Inversely proportional to the cube means F = kr3
- Substitute F = 6 and r = 2: 6 = k8, so k = 48
Answer: F = 48r3
Part (b)
- 3072 = 48r3, so r3 = 48 ÷ 3072 = 164
- r = ∛(164) = 14
Answer: r = 0.25
P is inversely proportional to y2. When y = 4, P = a.
(a) Find a formula for P in terms of y and a. (3)
Given also that y is directly proportional to √x and when x = a, P = 4a
(b) find a formula for P in terms of x and a. (3)
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Part (a)
- P = ky2
- a = k16, so k = 16a
Answer: P = 16ay2
Part (b)
- When P = 4a: 4a = 16ay2, so y2 = 4 and y = 2 (this is when x = a)
- y = m√x: 2 = m√a, so m = 2√a and y = 2√x√a
- y2 = 4xa. Substitute into part (a): P = 16a ÷ 4xa = 16a24x
Answer: P = 4a2x
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