Tommy, Riordan and Caden started walking at the same time from the same starting point round a circular track. Caden walked in the clockwise direction. Tommy and Riordan walked in an anti-clockwise direction. Caden took 6 min to complete each round. He met Tommy after every 2 minutes. He met Riordan after every 4 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 Tommy met again at the starting point after 1 h, Riordan had completed 1.4 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 : Tommy's distance
2 : 6 - 2
2 : 4

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

Caden	Tommy	Riordan
2x2	4x2
4x1		2x1
4	8	2

The distance of Caden is the repeated identity. 
LCM of 2 and 4 = 4

In 1 h
Caden's rounds : Tommy's rounds : Riordan's rounds
4 : 8 : 2

Distance that Riordan completed in 1 h = 1.4 km

2 rounds = 1.4 km = 1400 m

1 round = 1400 ÷ 2 = 700 m

Circumference of the circular track = 700 m

Answer(s): (a) 10; (b) 700 m