Simon, Ryan and Zane started walking at the same time from the same starting point round a circular track. Zane walked in the clockwise direction. Simon and Ryan walked in an anti-clockwise direction. Zane took 5 min to complete each round. He met Simon after every 3 minutes. He met Ryan after every 4 minutes. The three friends kept to their respective speeds throughout their walk.
- How many rounds did Zane complete in 1 h?
- When Zane and Simon met again at the starting point after 1 h, Ryan had completed 1.8 km. Find the circumference of the circular track in metres.
(a)
1 h = 60 min
Number of rounds that Zane completed in 1 h
= 60 ÷ 5
= 12
(b)
Zane took 5 min to complete 1 round
1 min =
15 of circular track = 1 u
5 min =
55 of circular track = 5 u
Zane's distance is the repeated identity.
Make Zane's distance the same.
Zane's distance : Simon's distance
3 : 5 - 3
3 : 2
Zane's distance : Ryan's distance
4 : 5 - 4
4 : 1
Zane |
Simon |
Ryan |
3x4 |
2x4 |
|
4x3 |
|
1x3 |
12 |
8 |
3 |
The distance of Zane is the repeated identity.
LCM of 3 and 4 = 12
In 1 h
Zane's rounds : Simon's rounds : Ryan's rounds
12 : 8 : 3
Distance that Ryan completed in 1 h = 1.8 km
3 rounds = 1.8 km = 1800 m
1 round = 1800 ÷ 3 = 600 m
Circumference of the circular track = 600 m
Answer(s): (a) 12; (b) 600 m