GATE Mechanical 2014 Set 3 | GA | Question: 8

Question

A man can row at $8$ $km$ per hour in still water. If it takes him thrice as long to row upstream, as to
row downstream, then find the stream velocity in $km$ per hour.

Answer 1

Let stream speed = v

Upstream speed = 8 − v
Downstream speed = 8 + v
Time upstream = 3 × time downstream

For same distance:

Distance / (8 − v) = 3 × Distance / (8 + v)

1 / (8 − v) = 3 / (8 + v)

8 + v = 3(8 − v)
8 + v = 24 − 3v
4v = 16
v = 4