A man swims downstream 72 km and upstream 45 km taking 9 hours each time; what is the speed of the current?

A. 3 kmph
B. 1.5 kmph
C. 13 kmph
D. 6.5 kmph
Explanation:
72 — 9 DS = 8
? —- 1
45 —- 9 US = 5
? —- 1 S = ?
S = (8 – 5)/2 = 1.5