Luke, Julian and Zeph started walking at the same time from the same starting point round a circular track. Zeph walked in the clockwise direction. Luke and Julian walked in an anti-clockwise direction. Zeph took 6 min to complete each round. He met Luke after every 2 minutes. He met Julian after every 4 minutes. The three friends kept to their respective speeds throughout their walk.
- How many rounds did Zeph complete in 1 h?
- When Zeph and Luke met again at the starting point after 1 h, Julian had completed 1.6 km. Find the circumference of the circular track in metres.
(a)
1 h = 60 min
Number of rounds that Zeph completed in 1 h
= 60 ÷ 6
= 10
(b)
Zeph took 6 min to complete 1 round
1 min =
16 of circular track = 1 u
6 min =
66 of circular track = 6 u
Zeph's distance is the repeated identity.
Make Zeph's distance the same.
Zeph's distance : Luke's distance
2 : 6 - 2
2 : 4
Zeph's distance : Julian's distance
4 : 6 - 4
4 : 2
Zeph |
Luke |
Julian |
2x2 |
4x2 |
|
4x1 |
|
2x1 |
4 |
8 |
2 |
The distance of Zeph is the repeated identity.
LCM of 2 and 4 = 4
In 1 h
Zeph's rounds : Luke's rounds : Julian's rounds
4 : 8 : 2
Distance that Julian completed in 1 h = 1.6 km
2 rounds = 1.6 km = 1600 m
1 round = 1600 ÷ 2 = 800 m
Circumference of the circular track = 800 m
Answer(s): (a) 10; (b) 800 m