Cathy and Zara started off at the same spot and ran at average speeds round a 3-km circular path. Cathy took 15 minutes to complete each round. Zara completed each round in 20 minutes.
- How far ahead of Zara would Cathy be after 1 minute? Express your answer in metres.
- How long would it take Cathy to meet Zara for the first time?
- How many rounds would Cathy have completed by then?
(a)
Cathy's speed =
315 =
15 km/min
Zara's speed =
320 km/min
Difference in speeds
=
15 -
320=
420 -
320=
120 km/min
Distance between Cathy and Zara after 1 min
= 1 x
120=
120 km
1 km = 1000 m
120 km =
120 x 1000 = 50
(b)
LCM of 15 and 20 = 60
60 min = 1 h
60 min = 60 ÷ 60 = 1
Cathy and Zara will meet for the first time after 1 h.
(c)
Rounds Cathy completed
= 60 ÷ 15
= 4
Answer(s): (a) 50 m; (b) 1 h; (c) 4