Ryan, Sean and Julian started walking at the same time from the same starting point round a circular track. Julian walked in the clockwise direction. Ryan and Sean walked in an anti-clockwise direction. Julian took 12 min to complete each round. He met Ryan after every 3 minutes. He met Sean after every 6 minutes. The three friends kept to their respective speeds throughout their walk.
- How many rounds did Julian complete in 1 h?
- When Julian and Ryan met again at the starting point after 1 h, Sean had completed 1.8 km. Find the circumference of the circular track in metres.
(a)
1 h = 60 min
Number of rounds that Julian completed in 1 h
= 60 ÷ 12
= 5
(b)
Julian took 12 min to complete 1 round
1 min =
112 of circular track = 1 u
12 min =
1212 of circular track = 12 u
Julian's distance is the repeated identity.
Make Julian's distance the same.
Julian's distance : Ryan's distance
3 : 12 - 3
3 : 9
Julian's distance : Sean's distance
6 : 12 - 6
6 : 6
Julian |
Ryan |
Sean |
3x2 |
9x2 |
|
6x1 |
|
6x1 |
6 |
18 |
6 |
The distance of Julian is the repeated identity.
LCM of 3 and 6 = 6
In 1 h
Julian's rounds : Ryan's rounds : Sean's rounds
6 : 18 : 6
Distance that Sean completed in 1 h = 1.8 km
6 rounds = 1.8 km = 1800 m
1 round = 1800 ÷ 6 = 300 m
Circumference of the circular track = 300 m
Answer(s): (a) 5; (b) 300 m