GCSE · Direct & inverse proportion

Direct proportionExam-style questions

Why "directly proportional" means multiplied by a fixed number, how the unitary method and the formula y = kx are the same idea, and how to spot when a relationship is (and isn't) direct proportion.

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13 questions · GCSE (Higher) level · mark scheme and worked solution on each · no sign-up to try

DifficultyAll Level 1 Level 2 Level 3 Level 4 Level 5

1
$5$ pens cost £ $1.20$ . How much do $8$ pens cost?
Level 1 · 2 marksTry it
2
$y$ is directly proportional to $x$ .

When $x = 4$ , $y = 18$

Work out the value of $y$ when $x = 10$ (3 marks)
Level 2 · 3 marksTry it
3
$y$ is directly proportional to the square root of $x$ .

When $x = 9$ , $y = 12$

Work out the value of $y$ when $x = 25$ (3 marks)
Level 2 · 3 marksTry it
4
$5$ identical pens cost £ $3.20$ .

Work out the cost of $8$ of these pens.
Level 2 · 2 marksTry it
5
A recipe for $12$ biscuits needs $150$ g of flour and $100$ g of butter.

Priya has $400$ g of flour and $250$ g of butter.

Work out the greatest number of biscuits Priya can make. You must show your working. [3]
Level 3 · 3 marksTry it

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