RATE AND SPEED
Rate
A factory worker is paid $64 for working 8 hours.
For 1 hour, he is paid $64
8
= $8.
He is paid the rate of $8 per hour.
Example:
A typist types at the rate of 45 words per minute. How long will she take to type 3
sheets of notes if there are 180 words in each sheet of paper?
Number of words on 1 sheet of paper = 180
Number of words on 3 sheets of paper = 180 x 3
= 540
Typing rate = 45 words per minute
Time taken to type 540 words = 540
45
= 12 minutes
She will take 12 minutes to type 3 sheets of notes.
Speed
When a motorist travels 75 kilometres in l hour, we say that he is travelling at a
speed of 75 km/h.
Average speed = Distance
Time
Distance travelled = Speed x Time
Time taken = Distance
Speed
Examples:
1. A car travelled at an average speed of 65 km/h for 2 ½ hours. How far did it
travel?
Distance |
Time |
Speed |
(a) |
2 ½ h |
65 km/h |
Time taken to travel = 2 ½ h
Average speed = 65 km/h
Total distatance travelled = 2 ½ x 65
= 5/2 x 65
= 325
2
= 162 ½ km or 162.5 km …………………. (a)
2. At an average speed of 75 km/h, how long will it take a car to travel 300 km?
Distance |
Time |
Speed |
300 km |
(a) |
75 km/h |
Total distance travelled = 300 km
Average speed = 75 km/h
Time taken to travel 300 km = 370
75
= 4h ……………………….. (a)
3. A van travelled 288 km in 6 hours. Find its average speed in km/h.
4. Mr Johari took 2 hours to drive from Town X to Town Y at an average speed of 50
km/h. He took another 2 1/2 hours to drive from Town Y to Town Z at an average speed
of 60 km/h. Find the total distance travelled by Mr Johari.
