Diana and Shiyun started off at the same spot and ran at average speeds round a 3-km circular path. Diana took 15 minutes to complete each round. Shiyun completed each round in 20 minutes.
- How far ahead of Shiyun would Diana be after 10 minute? Express your answer in metres.
- How long would it take Diana to meet Shiyun for the first time?
- How many rounds would Diana have completed by then?
(a)
Diana's speed =
315 =
15 km/min
Shiyun's speed =
320 km/min
Difference in speeds
=
15 -
320=
420 -
320=
120 km/min
Distance between Diana and Shiyun after 10 min
= 10 x
120=
1020 km
1 km = 1000 m
1020 km =
1020 x 1000 = 500
(b)
LCM of 15 and 20 = 60
60 min = 1 h
60 min = 60 ÷ 60 = 1
Diana and Shiyun will meet for the first time after 1 h.
(c)
Rounds Diana completed
= 60 ÷ 15
= 4
Answer(s): (a) 500 m; (b) 1 h; (c) 4