Question

A man rows to a place 35 km in distant and back in 10 hours 30 minutes. He found that he could row 5 km with the stream in the same time as he can row 4 km against the stream. Find the rate of flow of the stream:

Options

• 1 km/hr

• 0.5 km/hr

• 0.75 km/hr

• 1.5 km/hr

Answer 1

0.75 km/hr

Explanation:

`5/(x + y) = 4/(x - y)`

⇒ `5x - 5y = 4x + 4y`

⇒ `x = 9y`

Now, `35/(x + y) + 35/(x - y) = 21/2` h

⇒ `35[1/(10y) + 1/(8y)] = 21/2`

⇒ `(35 xx 9)/(40y) = 21/2`

⇒ `y` = 0.75 kmph