Xuan and David started running together along a cross country track. When David completed the track in 38 minutes, Xuan had run only
49 of the track. Xuan’s average speed was 115 m/min slower than David’s.
- How long was the cross country track in m?
- Find Xuan’s average speed in m/min.
(a)
When David completed the track:
David's distance = 9 u
Xuan's distance = 4 u
Extra distance covered by David
= 9 u - 4 u
= 5 u
5 u = 115 x 38
5 u = 4370
1 u = 4370 ÷ 5 = 874
Distance of the cross country track
= 9 u
= 9 x 874
= 7866 m
(b)
David's speed
= 7866 ÷ 38
= 207 m/min
Xuan's speed
= 207 - 115
= 92 m/min
Answer(s): (a) 7866 m; (b) 92 m/min