Question

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

Answer 1

Speed of the boat in water =.5 km/hr

Let the speed of the stream be x km/hr

So, the speed of the boat upstream will be (5-x) km / hr

So, the speed of the boat downstream is (5+x) k/hr

Time given to cover 40 km upstream = 3(time taken to cover dowmstream)

⇒40/ (5-x) km/hr = 3(5+x)

⇒1/(5-x)=3(5+x)

⇒5+x=15-3x

⇒x+3x=15-5

⇒4x=10

⇒X=10/4

⇒X=5/2

∴x=2.5 km/hr