Abi and Justin started off from the same place and drove at uniform speeds in the same direction round a 30 km circular racing track. Abi completed each round in 60 minutes. Justin took 90 minutes to complete each round.
- How far would Justin be behind Abi after 1 hour?
- How long after they started would it take Abi to meet Justin for the first time? Express your answer as a whole or mixed number in h.
(a)
60 min = 1 h
1 min =
160 h
60 min =
6060 h = 1 h
90 min =
9060 h = 1
12 h
Abi's speed
= 30 ÷ 1
= 30 x
11= 30 km/h
Justin's speed
= 30 ÷ 1
12= 30 x
23= 20 km/h
Distance between Abi and Justin after 1 hour
= 30 - 20
= 10 km
(b)
LCM of 60 and 90 = 180
180 min =
18060 h = 3 h
Time needed for Abi to meet Justin for the first time = 3 h
Answer(s): (a) 10 km; (b) 3 h