Speed, distance and time
You learn to work out how far someone goes when you know the speed and the time.
How to work it out
- Read the speed: that is how many km you travel in 1 hour, and 1 hour is 60 minutes.
- For whole hours, multiply the km by the number of hours.
- For minutes, find which part of the hour it is, and take that part of the km.
60
20
90
30
A worked example
A cyclist goes 16 km per hour. How far does he go in 3 hours?
- Read the speed: in 1 hour he goes 16 km.
- Multiply by 3 hours: 3 × 16 = 48.
- He goes 48 km.
More examples
A car goes 60 km per hour. How far does it go in 30 minutes?
- Find what part of the hour it is: 30 minutes is 12 hour.
- Take half: 60 ÷ 2 = 30.
- It goes 30 km.
A cyclist goes 18 km per hour. How far does he go in 40 minutes?
- Find what part of the hour it is: 40 minutes is 23 hour.
- Take 13: 18 ÷ 3 = 6.
- Multiply by 2: 2 × 6 = 12.
- He goes 12 km.
Watch out
You multiply the speed by the number of minutes: 60 × 30.
The speed is per hour, not per minute. First work out what part of the hour it is.
You think 30 minutes is 0.30 hour.
An hour is 60 minutes. 30 minutes is half an hour: 0.5 hour.
Tips
- Speed is per hour: first work out what part of the hour it is.
Why it works
16 km per hour means: every hour you go 16 km further. In 3 hours that is 3 times as far. If it takes less than an hour, you only go part of that 16 km.