MEASURES AND TIME

Speed Distance Time

Learn the reliable method for speed distance time, then apply it to 11+ exam-style questions.

1 · WHAT YOU NEED TO KNOW

The idea

Speed Distance Time questions combine accurate calculation with careful use of units.

Picture itConnect the number to its unit and scale
2 · THE METHOD

Follow these steps

  1. Read every unit before calculating.
  2. Convert all values to the same unit.
  3. Complete the operation, then give the answer in the unit requested.
3 · WORKED EXAMPLES

See the method in action

Example 1

A candle is 50 cm tall and burns down at 10 mm per hour. How many hours will it take to reach half its original height?

  1. Half the height is 25 cm = 250 mm.
  2. At 10 mm per hour, the time is 250 ÷ 10 = 25 hours.
Answer: 25 hours
Example 2

The dial shows a vehicle's constant speed. How far will it travel in 90 minutes?

0481216km/h
  1. First read 11 km/h from the scale.
  2. Convert 90 minutes to 90/60 hour, then calculate 11 × 90/60 = 16.5 km.
Answer: 16.5 km
4 · ELEVENSPRINT TIP

A useful shortcut

Convert first, calculate second.

5 · COMMON MISTAKES

Watch out for these

Using the wrong conversion factor

Use 1,000 between kg and g, litres and ml, and km and m; use 100 between m and cm.

6 · TRY IT YOURSELF

Three fresh questions

Ready to check the method? You will get three fresh, validated questions.