Worked Example 4: Speed and Time

Part of Proportion · Section 10 of 16

Study NotesUnit: NumberGCSE

This study notes covers Worked Example 4: Speed and Time within Proportion for GCSE Mathematics. Revise Proportion in Number for GCSE Mathematics with 12 exam-style questions and 22 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 10 of 16 in this topic. Use this study notes to connect the idea to the wider topic before moving on to questions and flashcards.

Worked Example 4: Speed and Time

For a journey of fixed distance, time is inversely proportional to speed. At 60 mph, the journey takes 2 hours. How long at 40 mph?

Solution

T ∝ 1/S, so T = k/S

When S = 60, T = 2: 2 = k/60

k = 2 × 60 = 120

So T = 120/S

When S = 40: T = 120/40 = 3

Answer: 3 hours

Practice questions for Proportion

y is directly proportional to x. Which equation could represent this relationship?

A. y = k/x
B. y = kx
C. y = k − x
D. y = x²

1 markfoundation

Explain how you can tell from a graph whether two quantities are in direct or inverse proportion.

2 marksstandard

Quick recall flashcards

Recipe Application

Recipe for 4 people uses 300g flour How much for 10 people? Flour ∝ People (direct) F = kP 300 = k × 4, so k = 75 For 10 people: F = 75 × 10 = 750g

Proportion Symbol

∝ means 'proportional to' Examples: y ∝ x (y is proportional to x) y ∝ 1/x (y is inversely proportional to x)

Worked Example 3: Recipe Scaling

Worked Example 5: Square Relationships

12 questions on Proportion — practise free

Instant marking, adaptive difficulty and spaced-repetition flashcards — all aligned to your exam board.

Start revising free →