Risa and Carl started running together along a cross country track. When Carl completed the track in 20 minutes, Risa had run only
38 of the track. Risa’s average speed was 95 m/min slower than Carl’s.
- How long was the cross country track in m?
- Find Risa’s average speed in m/min.
(a)
When Carl completed the track:
Carl's distance = 8 u
Risa's distance = 3 u
Extra distance covered by Carl
= 8 u - 3 u
= 5 u
5 u = 95 x 20
5 u = 1900
1 u = 1900 ÷ 5 = 380
Distance of the cross country track
= 8 u
= 8 x 380
= 3040 m
(b)
Carl's speed
= 3040 ÷ 20
= 152 m/min
Risa's speed
= 152 - 95
= 57 m/min
Answer(s): (a) 3040 m; (b) 57 m/min