Cody, Mark and Caden started walking at the same time from the same starting point round a circular track. Caden walked in the clockwise direction. Cody and Mark walked in an anti-clockwise direction. Caden took 6 min to complete each round. He met Cody after every 4 minutes. He met Mark after every 5 minutes. The three friends kept to their respective speeds throughout their walk.

1. How many rounds did Caden complete in 1 h?
2. When Caden and Cody 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 Caden completed in 1 h
= 60 ÷ 6
= 10

(b)
Caden took 6 min to complete 1 round
1 min = ¹₆ of circular track = 1 u
6 min = ⁶₆ of circular track = 6 u

Caden's distance is the repeated identity.
Make Caden's distance the same.

Caden's distance : Cody's distance
4 : 6 - 4
4 : 2

Caden's distance : Mark's distance
5 : 6 - 5
5 : 1

Caden	Cody	Mark
4x5	2x5
5x4		1x4
20	10	4

The distance of Caden is the repeated identity. 
LCM of 4 and 5 = 20

In 1 h
Caden's rounds : Cody's rounds : Mark's rounds
20 : 10 : 4

Distance that Mark completed in 1 h = 2.2 km

4 rounds = 2.2 km = 2200 m

1 round = 2200 ÷ 4 = 550 m

Circumference of the circular track = 550 m

Answer(s): (a) 10; (b) 550 m