Question

A man rowing at the rate of 5 km in an hour 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

Hey there!

Answer:

2.5 km/hr

Step-by-step explanation:

Let the rate of stream be x.

Time taken by upstream = 40 / (5-a)

Time taken by downstream = 40 / (5+a)

According to Question,

40 / (5-a) = 3 [40 /( 5+a)]

or, 40 / (5-a) = 120 / (5+a)

or,  40 ( 5+a) = 120 (5-a)

or, 200 + 40a = 600 - 120a

or, 40a + 120a = 600 - 200

or,  160a = 400

or,  a = 400/160

or, a = 2.5

Hence, rate at which river flows is 2.5 km/hr.

Hope It Helps You!