Oliver, Michael and Peter started walking at the same time from the same starting point round a circular track. Peter walked in the clockwise direction. Oliver and Michael walked in an anti-clockwise direction. Peter took 6 min to complete each round. He met Oliver after every 4 minutes. He met Michael after every 5 minutes. The three friends kept to their respective speeds throughout their walk.
- How many rounds did Peter complete in 1 h?
- When Peter and Oliver met again at the starting point after 1 h, Michael had completed 1.3 km. Find the circumference of the circular track in metres.
(a)
1 h = 60 min
Number of rounds that Peter completed in 1 h
= 60 ÷ 6
= 10
(b)
Peter took 6 min to complete 1 round
1 min =
16 of circular track = 1 u
6 min =
66 of circular track = 6 u
Peter's distance is the repeated identity.
Make Peter's distance the same.
Peter's distance : Oliver's distance
4 : 6 - 4
4 : 2
Peter's distance : Michael's distance
5 : 6 - 5
5 : 1
Peter |
Oliver |
Michael |
4x5 |
2x5 |
|
5x4 |
|
1x4 |
20 |
10 |
4 |
The distance of Peter is the repeated identity.
LCM of 4 and 5 = 20
In 1 h
Peter's rounds : Oliver's rounds : Michael's rounds
20 : 10 : 4
Distance that Michael completed in 1 h = 1.3 km
4 rounds = 1.3 km = 1300 m
1 round = 1300 ÷ 4 = 325 m
Circumference of the circular track = 325 m
Answer(s): (a) 10; (b) 325 m