Usha and Jack started off from the same place and drove at uniform speeds in the same direction round a 40 km circular racing track. Usha completed each round in 80 minutes. Jack took 100 minutes to complete each round.
- How far would Jack be behind Usha after 1 hour?
- How long after they started would it take Usha to meet Jack for the first time? Express your answer as a whole or mixed number in h.
(a)
60 min = 1 h
1 min =
160 h
80 min =
8060 h = 1
13 h
100 min =
10060 h = 1
23 h
Usha's speed
= 40 ÷ 1
13= 40 x
34= 30 km/h
Jack's speed
= 40 ÷ 1
23= 40 x
35= 24 km/h
Distance between Usha and Jack after 1 hour
= 30 - 24
= 6 km
(b)
LCM of 80 and 100 = 400
400 min =
40060 h = 6
23 h
Time needed for Usha to meet Jack for the first time = 6
23 h
Answer(s): (a) 6 km; (b) 6
23 h