A man takes twice as long to row a distance against the stream as to row the same distance in favour of the stream. The ratio of the speed of the boat(in still water) and the stream is:

A. 1:2
B. 1:3
C. 2:1
D. 3:1
Ans: D

Explanation:

Let man’s rate upstream be x kmph. Then, his rate downstream = 2x kmph.
=> (Speed in still water) : (Speed of stream)
= [2x + x / 2] : [2x - x / 2]
3x / 2 : x / 2 = 3:1