Question

Ques. a boat covers 40 km upstream and 90 km downstream in 5 hr. it can also cover 60 km upstream and 60 km downstream in 5 hr. the speed of the water current is

Answer 1

The speed of water current is 5 km/hr.

Let speed of boat in still water be b km/hr & speed of water current be w km/hr;
Since s=d/t; => t=d/s
(40/(b-w)+90/(b+w))=5;______(Eq.1) (60/(b-w)+60/(b+w))=5;_________(Eq.2)
on solving Eq.1 & Eq.2 we get b=5w and then substitute this in any one of the above eqn we get w=5 km/hr