Speed, distance & time

Speed, distance and time are connected by a formula triangle. Given any two, you can find the third.

Revising speed, distance & time the night before an exam? These are condensed revision notes — the facts, formulas and mistakes examiners actually mark, with no long explanations. Prefer a full walkthrough with step-by-step reasoning instead? Search “Speed, distance & time GCSE” on the site for the complete guide.

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Key facts to remember

1Speed = Distance ÷ Time
2Distance = Speed × Time
3Time = Distance ÷ Speed
4Units must be consistent (e.g. km/h and hours, or m/s and seconds).
5Average speed = total distance ÷ total time (not the mean of two speeds).

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Formulas

Speed

S = D/T

Distance

D = S × T

Time

T = D/S

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Worked examples

Example 1

A car travels 180 km at an average speed of 60 km/h. How long does the journey take?

Working

Time = Distance ÷ Speed
T = 180 ÷ 60 = 3 hours

Answer3 hours

Example 2

A runner completes 400 m in 50 seconds. Find their speed in m/s.

Working

Speed = Distance ÷ Time
S = 400 ÷ 50 = 8 m/s

Answer8 m/s

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Common mistakes

✗Using inconsistent units (e.g. distance in km but time in minutes).

✗Dividing speed by distance instead of distance by speed for time.

✗Calculating average speed as the mean of two speeds rather than total distance ÷ total time.

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Exam tips

✓Use the formula triangle — cover the quantity you want to find.

✓Convert units before calculating: minutes → hours (÷ 60), metres → km (÷ 1000).

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