A boat covers 45 km upstream and 60 km downstream in 15 hours. It also covers 30 km upstream and 40 km downstream in 10 hours. Find the speed of the stream.

Question

Accepted Answer

(C) 5 km/h. Explanation: Let upstream speed = u, downstream = d. 45/u + 60/d = 15 and 30/u + 40/d = 10 — both give 3/u + 4/d = 1. Stream = (d-u)/2 = 5 km/h.