Charlie, Neave and Ahmad started walking at the same time from the same starting point round a circular track. Ahmad walked in the clockwise direction. Charlie and Neave walked in an anti-clockwise direction. Ahmad took 6 min to complete each round. He met Charlie after every 2 minutes. He met Neave after every 4 minutes. The three friends kept to their respective speeds throughout their walk.

1. How many rounds did Ahmad complete in 1 h?
2. When Ahmad and Charlie met again at the starting point after 1 h, Neave had completed 1.4 km. Find the circumference of the circular track in metres.

(a)
1 h = 60 min

Number of rounds that Ahmad completed in 1 h
= 60 ÷ 6
= 10

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

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

Ahmad's distance : Charlie's distance
2 : 6 - 2
2 : 4

Ahmad's distance : Neave's distance
4 : 6 - 4
4 : 2

Ahmad	Charlie	Neave
2x2	4x2
4x1		2x1
4	8	2

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

In 1 h
Ahmad's rounds : Charlie's rounds : Neave's rounds
4 : 8 : 2

Distance that Neave 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