Question

A man takes half time in rowing a certain distance downstream than upstream. What is the ratio of the speed in still water to the speed of current?

(a) 1:2

(b) 2:1

(c) 1:3

(d) 3:1

Answer 1

Correct option is (d) 3:1

Let the speed of the boat in still water is x km/h

And the speed of the stream is y km/h.

⇒ Downstream = (x + y) km/h

⇒ Upstream = (x - y) km/h

Ratio of time downstream : upstream = 1 : 2

Ratio of speed downstream : upstream = 2 : 1

⇒ (x + y) : (x - y) = 2 : 1

⇒ x + y = 2x - 2y

⇒ x = 3y

⇒ x/y = 3/1

Speed of the boat in still water :  Speed of stream = 3 : 1