Roshel and Lucy started off at the same spot and ran at average speeds round a 3-km circular path. Roshel took 15 minutes to complete each round. Lucy completed each round in 20 minutes.
- How far ahead of Lucy would Roshel be after 5 minute? Express your answer in metres.
- How long would it take Roshel to meet Lucy for the first time?
- How many rounds would Roshel have completed by then?
(a)
Roshel's speed =
315 =
15 km/min
Lucy's speed =
320 km/min
Difference in speeds
=
15 -
320=
420 -
320=
120 km/min
Distance between Roshel and Lucy after 5 min
= 5 x
120=
520 km
1 km = 1000 m
520 km =
520 x 1000 = 250
(b)
LCM of 15 and 20 = 60
60 min = 1 h
60 min = 60 ÷ 60 = 1
Roshel and Lucy will meet for the first time after 1 h.
(c)
Rounds Roshel completed
= 60 ÷ 15
= 4
Answer(s): (a) 250 m; (b) 1 h; (c) 4