Question

A boat coves a distance of 60km downstream in one and half hours. It covers the same distance upstream in 2hours. If the speed of the boat in still water is 35km/hr. Find the speed of the stream.

Answer 1

As the speed of the boat in still water is known to us we can calculate the speed of the stream either any stream i.e. down stream or up stream.

Say, the speed of the stream is x km/hr.

Going downstream the speed of the boat and the speed of the stream will be added together i. e. ( 35 + x ) km/hr

Hence the boat goes ( 35 + x ) km in 1 hr.

For a distance of 60 km, the Time = 60 /( 35 + x ) hr

so, 60 /( 35 + x ) = 1+1/2 = 3/2

or, 3( 35+ x ) = 120

or, 3x = 120 - 105

or, x = 15/3 = 5

Speed of the stream is 5 km/hr.