1. SPEED, DISTANCE AND TIME

2. Changing units of time 1 Write 24 minutes as a fraction of an hour.
to change minutes into hours divide by 60
2 Write 54 minutes as a decimal of an hour.
54 minutes =
to change minutes into hours divide by 60
to change a fraction to a decimal divide the numerator by the denominator

3. 3 Change of an hour into minutes.
to change hours into minutes multiply by 60
4 Change 0.3 hours into minutes.
to change hours into minutes multiply by 60

4. Speed Speed is a measure of how fast an object is travelling.
When the speed is constant, the formula connecting speed, distance and time is:
If the distance is measured in metres and the time is measured in seconds then the speed is measured in metres per second (m/s or ms−1).
If the distance is measured in kilometres and the time is measured in hours then the speed is measured in kilometres per hour (km/h or kmh−1).

5. 1 A car takes 3 hours 20 minutes to travel 300 km at constant speed.
Find the speed of the car in km/h.
You must first change 20 minutes into hours.

6. 2 A car is travelling at 54 km/h.
Change the speed of the car into m/s.
54 kilometres/hour =
metres/hour

7. D S × T The formula can be rearranged to give distance = speed × time
The following triangle is a useful memory aid for remembering the three formulae.
To find the formula for finding T put your finger over the letter T. D
S × T
This gives you
To find the formula for finding D put your finger over the letter D.
This gives you

8. A bird flies for 48 km at a speed of 6 m/s.
Calculate the time taken in hours and minutes.
change 48 km into m
48 km = m
divide by 60 to change into minutes
120 minutes = 2 hours

9. Average speed
You can calculate the average speed for a journey using:

10. A car travels at 75 km/h for 3 hours and then at 60 km/h for 30 minutes.
a Calculate the total distance travelled.
b Calculate the average speed for the whole journey.
a distance = speed × time
Total distance = = 255 km b