Zara and David started off from the same place and drove at uniform speeds in the same direction round a 45 km circular racing track. Zara completed each round in 50 minutes. David took 90 minutes to complete each round.
- How far would David be behind Zara after 1 hour?
- How long after they started would it take Zara 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
50 min =
5060 h =
56 h
90 min =
9060 h = 1
12 h
Zara's speed
= 45 ÷
56= 45 x
65= 54 km/h
David's speed
= 45 ÷ 1
12= 45 x
23= 30 km/h
Distance between Zara and David after 1 hour
= 54 - 30
= 24 km
(b)
LCM of 50 and 90 = 450
450 min =
45060 h = 7
12 h
Time needed for Zara to meet David for the first time = 7
12 h
Answer(s): (a) 24 km; (b) 7
12 h