Ivory and David started off from the same place and drove at uniform speeds in the same direction round a 40 km circular racing track. Ivory completed each round in 60 minutes. David took 80 minutes to complete each round.
- How far would David be behind Ivory after 1 hour?
- How long after they started would it take Ivory to meet David 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
80 min =
8060 h = 1
13 h
Ivory's speed
= 40 ÷ 1
= 40 x
11= 40 km/h
David's speed
= 40 ÷ 1
13= 40 x
34= 30 km/h
Distance between Ivory and David after 1 hour
= 40 - 30
= 10 km
(b)
LCM of 60 and 80 = 240
240 min =
24060 h = 4 h
Time needed for Ivory to meet David for the first time = 4 h
Answer(s): (a) 10 km; (b) 4 h