Ivory and Mark started off from the same place and drove at uniform speeds in the same direction round a 30 km circular racing track. Ivory completed each round in 40 minutes. Mark took 60 minutes to complete each round.
- How far would Mark be behind Ivory after 1 hour?
- How long after they started would it take Ivory to meet Mark for the first time? Express your answer as a whole or mixed number in h.
(a)
60 min = 1 h
1 min =
160 h
40 min =
4060 h =
23 h
60 min =
6060 h = 1 h
Ivory's speed
= 30 ÷
23= 30 x
32= 45 km/h
Mark's speed
= 30 ÷ 1
= 30 x
11= 30 km/h
Distance between Ivory and Mark after 1 hour
= 45 - 30
= 15 km
(b)
LCM of 40 and 60 = 120
120 min =
12060 h = 2 h
Time needed for Ivory to meet Mark for the first time = 2 h
Answer(s): (a) 15 km; (b) 2 h