Unit 18 Section 2 : Calculating speed, distance and time
We saw in the previous section that speed, distance and time are all related.
In this section we look at calculating distances and times using the following formulae:
Example Question 1
Jane drives at an average speed of 45 mph on a journey of 135 miles.
How long does the journey take?
To find a time, we need to divide distance by speed.
135 miles ÷ 45 mph = 3 hours
Example Question 2
Chris cycles at an average speed of 8 mph.
If he cycles for 6½ hours, how far does he travel?
To find a distance, we need to multiply speed by time.
8 mph × 6.5 hours = 52 miles
Example Question 3
Nikki has to travel a total of 351 miles. She travels the first 216 miles in 4 hours.
(a) What is her average speed for the first part of the journey?
To find average speed, we need to divide distance by time.
216 miles ÷ 4 hours = 54 mph
Her average speed is the same for the whole of her journey.
(b) How long does the whole journey take?
To find time, we need to divide distance by speed.
351 miles ÷ 54 mph = 6.5 hours
Work out the answer to each of these questions then click on the button marked
to see whether you are correct.
Practice Question 1
Jim travels 45 miles at 15 mph.
How long does it take him?
Practice Question 2
Jemimah walks at 4 mph for 2½ hours.
How far does she walk?
Practice Question 3
Jenny drives at a constant speed. In the first three hours she travels 81 miles.
How far will she have travelled after 5 hours?