Luke, Mark and Neave started walking at the same time from the same starting point round a circular track. Neave walked in the clockwise direction. Luke and Mark walked in an anti-clockwise direction. Neave took 12 min to complete each round. He met Luke after every 2 minutes. He met Mark after every 7 minutes. The three friends kept to their respective speeds throughout their walk.
- How many rounds did Neave complete in 1 h?
- When Neave and Luke met again at the starting point after 1 h, Mark had completed 2.2 km. Find the circumference of the circular track in metres.
(a)
1 h = 60 min
Number of rounds that Neave completed in 1 h
= 60 ÷ 12
= 5
(b)
Neave took 12 min to complete 1 round
1 min =
112 of circular track = 1 u
12 min =
1212 of circular track = 12 u
Neave's distance is the repeated identity.
Make Neave's distance the same.
Neave's distance : Luke's distance
2 : 12 - 2
2 : 10
Neave's distance : Mark's distance
7 : 12 - 7
7 : 5
Neave |
Luke |
Mark |
2x7 |
10x7 |
|
7x2 |
|
5x2 |
14 |
70 |
10 |
The distance of Neave is the repeated identity.
LCM of 2 and 7 = 14
In 1 h
Neave's rounds : Luke's rounds : Mark's rounds
14 : 70 : 10
Distance that Mark completed in 1 h = 2.2 km
10 rounds = 2.2 km = 2200 m
1 round = 2200 ÷ 10 = 220 m
Circumference of the circular track = 220 m
Answer(s): (a) 5; (b) 220 m