Question

Boat 'A' takes 60 seconds to cover entire length of the river when travelling with the stream. Had the speed of the stream been double, then the boat would've saved 10 seconds to complete the same journey. Find the time taken by a hat that is floating in the river to cover the same distance, if the stream is flowing at the original speed.

• A. 150 seconds
• B. 75 seconds
• C. 300 seconds
• D. 225 seconds

Answer 1

The Correct Option is C

Let the speed of the boat in still water be 'x' m/s and speed of the stream be 'y' m/s.
Let the total distance be ’d’ metres
According to the question,
{d/(x + y)} = 60Or, d = 60 X (x + y) ........ (I)
Also, {d/(x + 2y)} = 60 – 10
Or, d = 50X (x + 2y) ....... (II)
On equating equation (I) and (II), we have;
60x + 60y = 50x + 100y
Or, 10x = 40y
So, x = 4y
According to the question,
d = 60 X (4y + y)
Or, d = 300y
So, required time = 300y ÷ y = 300 seconds
So, the correct option is (C) : 300 seconds.