Peter, Dylan and Reggie started walking at the same time from the same starting point round a circular track. Reggie walked in the clockwise direction. Peter and Dylan walked in an anti-clockwise direction. Reggie took 6 min to complete each round. He met Peter after every 4 minutes. He met Dylan after every 5 minutes. The three friends kept to their respective speeds throughout their walk.
- How many rounds did Reggie complete in 1 h?
- When Reggie and Peter met again at the starting point after 1 h, Dylan had completed 1.6 km. Find the circumference of the circular track in metres.
(a)
1 h = 60 min
Number of rounds that Reggie completed in 1 h
= 60 ÷ 6
= 10
(b)
Reggie took 6 min to complete 1 round
1 min =
16 of circular track = 1 u
6 min =
66 of circular track = 6 u
Reggie's distance is the repeated identity.
Make Reggie's distance the same.
Reggie's distance : Peter's distance
4 : 6 - 4
4 : 2
Reggie's distance : Dylan's distance
5 : 6 - 5
5 : 1
Reggie |
Peter |
Dylan |
4x5 |
2x5 |
|
5x4 |
|
1x4 |
20 |
10 |
4 |
The distance of Reggie is the repeated identity.
LCM of 4 and 5 = 20
In 1 h
Reggie's rounds : Peter's rounds : Dylan's rounds
20 : 10 : 4
Distance that Dylan completed in 1 h = 1.6 km
4 rounds = 1.6 km = 1600 m
1 round = 1600 ÷ 4 = 400 m
Circumference of the circular track = 400 m
Answer(s): (a) 10; (b) 400 m