Diana and Risa started off at the same spot and ran at average speeds round a 6-km circular path. Diana took 24 minutes to complete each round. Risa completed each round in 25 minutes.
- How far ahead of Risa would Diana be after 2 minute? Express your answer in metres.
- How long would it take Diana to meet Risa for the first time?
- How many rounds would Diana have completed by then?
(a)
Diana's speed =
624 =
14 km/min
Risa's speed =
625 km/min
Difference in speeds
=
14 -
625=
25100 -
24100=
1100 km/min
Distance between Diana and Risa after 2 min
= 2 x
1100=
2100 km
1 km = 1000 m
2100 km =
2100 x 1000 = 20
(b)
LCM of 24 and 25 = 600
60 min = 1 h
600 min = 600 ÷ 60 = 10
Diana and Risa will meet for the first time after 10 h.
(c)
Rounds Diana completed
= 600 ÷ 24
= 25
Answer(s): (a) 20 m; (b) 10 h; (c) 25