Question

A boat takes thrice the time in moving a certain distance upstream than downstream. Find the ratio of speed of boat in still water to that of speed of current.

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

Answer 1

Answer:

A. 2 : 1

Given:

Boat takes thrice the time in moving a certain distance downstream than upstream

Formula used:

Time Distance = Speed $\times$ Time

u = x + y, v = x – y;

where, u is speed of rowing downstream, v is speed of rowing upstream, x is speed in still water and y is speed of stream.

Calculation:

Here, distance is equal and because boat takes thrice the time in moving a certain distance downstream than upstream then if time in downstream is 1 then time in upstream is 3.

Thus, u $\times$ 1 = v $\times$ 3

⇒ (x + y) $\times$ 1 = (x – y) $\times$ 3

⇒ x + y = 3x – 3y

⇒ x = 2y

⇒ x : y = 2 : 1

⇒ Speed of boat in still water : speed of current = 2 : 1