Betty and Ethan started off from the same place and drove at uniform speeds in the same direction round a 35 km circular racing track. Betty completed each round in 60 minutes. Ethan took 70 minutes to complete each round.
- How far would Ethan be behind Betty after 1 hour?
- How long after they started would it take Betty to meet Ethan 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
70 min =
7060 h = 1
16 h
Betty's speed
= 35 ÷ 1
= 35 x
11= 35 km/h
Ethan's speed
= 35 ÷ 1
16= 35 x
67= 30 km/h
Distance between Betty and Ethan after 1 hour
= 35 - 30
= 5 km
(b)
LCM of 60 and 70 = 420
420 min =
42060 h = 7 h
Time needed for Betty to meet Ethan for the first time = 7 h
Answer(s): (a) 5 km; (b) 7 h