Speed · Usually met around P6
Comparing speeds
Same time: compare distance; same distance: compare time.
How to do it
Method
Same time: compare distance; same distance: compare time
240 ÷ 3 = 80, 350 ÷ 5 = 70: A is faster
Another way
Make the times equal
In 15 minutes: 1200 m against 1050 m
In full
To tell who is faster, look at how far each goes in the same time, or how long each takes for the same distance. Starting and stopping together, the one who goes further is faster. Over the same distance, the one who takes less time is faster. When both the times and distances differ, find how far each goes in one unit of time (the speed), in any unit you like: A goes 240 m in 3 minutes, 240 ÷ 3 = 80 m a minute; B goes 350 m in 5 minutes, 350 ÷ 5 = 70 m a minute; A is faster. Another way: make the times the same — in 15 minutes A goes 240 × 5 = 1200 m and B goes 350 × 3 = 1050 m. Looking only at the distance or only at the time isn't enough.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
Tsz-ching skips 618 times in 6 minutes. How many skips is that a minute, on average?
Show the answer and working
Answer: 103 skips
Skips a minute = skips ÷ minutes: 618 ÷ 6 = 103.
Example 2
A, B and C each run 100 m, taking 16, 12 and 17 seconds. Who is the fastest?
- A. B
- B. A
- C. All the same
- D. C
Choose the right answer
Show the answer and working
Answer: A. B
Over the same distance, whoever takes least time is fastest.
Example 3
A walks 330 m in 6 minutes and B walks 225 m in 3 minutes. How many more metres a minute does the faster one walk?
Show the answer and working
Answer: 20 m
A: 55 m a minute; B: 75 m a minute; 20 m apart.
Practise it in the game →Speed · Free to start, unlimited questions, no download