Speed, Distance, and Time

Calculate speed, distance, and time for GCSE Maths. Solve problems with average speed and unit conversions.

Speed, distance, and time are related by a simple formula. GCSE questions often involve calculating one quantity given the other two, working with different units, and finding average speed.

Core Formula

Speed=DistanceTime\text{Speed} = \frac{\text{Distance}}{\text{Time}}

Distance=Speed×Time\text{Distance} = \text{Speed} \times \text{Time}

Time=DistanceSpeed\text{Time} = \frac{\text{Distance}}{\text{Speed}}

Units

  • km/h, m/s, mph
  • km/h → m/s: ÷ 3.6 (or × 518\frac{5}{18})
  • m/s → km/h: × 3.6

Average Speed

Average speed=Total distanceTotal time\text{Average speed} = \frac{\text{Total distance}}{\text{Total time}}

Worked Example: Example 1

Problem

A car travels 150 km in 2.5 hours. Speed = 1502.5=60\frac{150}{2.5} = 60 km/h.

Solution

Worked Example: Example 2

Problem

A cyclist rides at 12 km/h for 45 minutes. Distance = 12×0.75=912 \times 0.75 = 9 km.

Solution

Worked Example: Example 3

Problem

Jan drives 100 km at 80 km/h, then 60 km at 40 km/h.

Total distance = 160 km. Total time = 10080+6040=1.25+1.5=2.75\frac{100}{80} + \frac{60}{40} = 1.25 + 1.5 = 2.75 hours.

Average speed = 1602.7558.2\frac{160}{2.75} \approx 58.2 km/h.

Solution

Practice Problems

    1. Distance 240 km, time 3 hours. Find speed.
    1. Speed 15 m/s for 2 minutes. Find distance.
    1. Convert 90 km/h to m/s.

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Key Takeaways

  • S=DTS = \frac{D}{T}, D=S×TD = S \times T, T=DST = \frac{D}{S}.

  • Average speed uses total distance and total time.

  • Watch units — convert minutes to hours if using km/h.

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