Mary and Zoe started off at the same spot and ran at average speeds round a 6-km circular path. Mary took 12 minutes to complete each round. Zoe completed each round in 25 minutes.
- How far ahead of Zoe would Mary be after 3 minute? Express your answer in metres.
- How long would it take Mary to meet Zoe for the first time?
- How many rounds would Mary have completed by then?
(a)
Mary's speed =
612 =
12 km/min
Zoe's speed =
625 km/min
Difference in speeds
=
12 -
625=
2550 -
1250=
1350 km/min
Distance between Mary and Zoe after 3 min
= 3 x
1350=
3950 km
1 km = 1000 m
3950 km =
3950 x 1000 = 780
(b)
LCM of 12 and 25 = 300
60 min = 1 h
300 min = 300 ÷ 60 = 5
Mary and Zoe will meet for the first time after 5 h.
(c)
Rounds Mary completed
= 300 ÷ 12
= 25
Answer(s): (a) 780 m; (b) 5 h; (c) 25