A man takes half time in rowing a certain distance downstream than upstream

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?

1. 1 : 2
2. 2 : 1
3. 1 : 3
4. 3 : 1

• Answer: The correct option is D
• Explanation:

  Method I:

  Let the speed of man in still water be x and the speed of current be y. Let the total distance be D.

  So, Downstream speed = x + y

  Upstream speed = x - y

  According to the question,

  Time taken in rowing upstream = 2 × Time taken in rowing downstream

  D/(x - y) = 2 × [D/(x + y)]

  x + y = 2x - 2y

  x = 3y ∴ x : y = 3 : 1

  Method II:

  If time taken half, then the speed must be double, as the distance is constant.

  So, x + y = 2(x - y)

  x = 3y

  x : y = 3 : 1

• Exam Year: 2020