# 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 Questions

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

## Practice Questions

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? ## Exercises

Work out the answers to the questions below and fill in the boxes. Click on the button to find out whether you have answered correctly. If you are right then will appear and you should move on to the next question. If appears then your answer is wrong. Click on to clear your original answer and have another go. If you can't work out the right answer then click on to see the answer.

Question 1
Calculate the distance that you would travel if you drove for:
 (a) 3 hours at 20 mph miles  (b) 8 hours at 60 mph miles  (c) ½ hour at 76 mph miles  (d) 1½ hours at 42 mph miles  Question 2
How long does it take to travel:
 (a) 120 miles at 40 mph? hours  (b) 300 miles at 50 mph? hours  (c) 240 miles at 60 mph? hours  (d) 385 miles at 70 mph? hours  Question 3
A car travels 300 miles in 5 hours.

(a) What is average speed of the car in miles per hour?
mph  (b) What is the average speed of the car in miles per minute?
miles per minute  (c) Assuming the speed is constant, how long does it take the car to travel 82 miles?
minutes  Question 4
Janet and Bill leave their home at the same time.
Janet has 60 miles to travel and drives at 40 mph.
Bill has 80 miles to travel and also drives at 40 mph.

(a) How long does Janet's journey take?
hours  (b) How much longer does Bill spend driving than Janet?
hours  Question 5
An athlete can run long distances at 4 metres per second.

How far can she run in:
 (a) 50 seconds? mk  (b) 3 minutes? mk  (c) 1 hour? km  (d) 2½ hours? km  Question 6
Andrew rows at an average speed of 2 metres per second.

(a) How long does it take him to row 70m?
s  (b) How long does it take him to row 800m?
 minutes and  seconds  (c) How far can he row in 12 seconds?
m  (d) How far can he row in 3½ minutes?
m  Question 7
A snail moves 5 metres in 2 hours.

If the snail moves at the same speed calculate:
(a) the time it takes to move 20 m
hours  (b) the distance it would move in 3½ hours
metres  (c) the time it takes to moves 1 m
minutes  You have now completed Unit 18 Section 2
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