Mark, Gabriel and Warren started walking at the same time from the same starting point round a circular track. Warren walked in the clockwise direction. Mark and Gabriel walked in an anti-clockwise direction. Warren took 5 min to complete each round. He met Mark after every 3 minutes. He met Gabriel after every 4 minutes. The three friends kept to their respective speeds throughout their walk.

1. How many rounds did Warren complete in 1 h?
2. When Warren and Mark met again at the starting point after 1 h, Gabriel had completed 1.8 km. Find the circumference of the circular track in metres.

(a)
1 h = 60 min

Number of rounds that Warren completed in 1 h
= 60 ÷ 5
= 12

(b)
Warren took 5 min to complete 1 round
1 min = ¹₅ of circular track = 1 u
5 min = ⁵₅ of circular track = 5 u

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

Warren's distance : Mark's distance
3 : 5 - 3
3 : 2

Warren's distance : Gabriel's distance
4 : 5 - 4
4 : 1

Warren	Mark	Gabriel
3x4	2x4
4x3		1x3
12	8	3

The distance of Warren is the repeated identity. 
LCM of 3 and 4 = 12

In 1 h
Warren's rounds : Mark's rounds : Gabriel's rounds
12 : 8 : 3

Distance that Gabriel completed in 1 h = 1.8 km

3 rounds = 1.8 km = 1800 m

1 round = 1800 ÷ 3 = 600 m

Circumference of the circular track = 600 m

Answer(s): (a) 12; (b) 600 m