Question

13. A man rowing at the rate of 5 km/h in still
water takes thrice as much time in going
40 km up the river as in going 40 km down.
Find the rate at which the river flows.​

Answer 1

Consider,

Speed of rowing by a person =5 km/hr.

Speed of stream =x km/hr

Upstream Speed =(5−x) km/hr

Downstream speed =(5+x) km/hr

According to the question,

⇒

5−x

40

=

5+x

3×40

⇒5+x=15−3x

⇒4x=10

⇒x=2.5 km/hr