Irene and Perry started running together along a cross country track. When Perry completed the track in 31 minutes, Irene had run only
13 of the track. Irene’s average speed was 100 m/min slower than Perry’s.
- How long was the cross country track in m?
- Find Irene’s average speed in m/min.
(a)
When Perry completed the track:
Perry's distance = 3 u
Irene's distance = 1 u
Extra distance covered by Perry
= 3 u - 1 u
= 2 u
2 u = 100 x 31
2 u = 3100
1 u = 3100 ÷ 2 = 1550
Distance of the cross country track
= 3 u
= 3 x 1550
= 4650 m
(b)
Perry's speed
= 4650 ÷ 31
= 150 m/min
Irene's speed
= 150 - 100
= 50 m/min
Answer(s): (a) 4650 m; (b) 50 m/min