Calculate Average Speed

Speed is an example of a compound measure because it involves more than one unit of measure. 

 

Speed is a measure of distance in relation to time . 

For example, a common one is the speed of a car. It is measured in mph or miles per hour or km/h kilometres per hour.

 

 

We can work this out in the first instance without a calculator if we look at average speed!

Let's say we set out in a car from home.

We travel at a constant speed, and after 1 hour we are 50 miles away from home.

 

We can say that our speed was 50 mph because it means 50 miles per 1 hour.

It does what it says on the tin!

30 mph means we can travel 30 miles in 1 hour.

 

Let's try a question.

 

Example

What is the average speed of a car which travels 80 miles in 2 hours?

 

Answer

If the car travels 80 miles in 2 hours, we want to know how far it has travelled in 1 hour for the average speed.

80 ÷ 2 = 40 miles in 1 hour

Therefore, the average speed is 40 mph.

 

Let's have a go at some questions!