Question

A swimmer, whose speed is 9 km/h in still water, goes 9 km downstream in 45 minutes. Find the speed of the stream.

Options

• 9 km/h

• 3 km/h

• 12 km/h

• 6 km/h

Answer 1

3 km/h

Explanation:

Let speed of stream = w

Speed of swimmer (S) = 9 km/h

Speed in downstream = (s + w) = (9 + w)

Now, From t he question, `9/(9 + w) = 45/60`

⇒ `9/(9 + w) = 3/4`

⇒ `(9 + w)` = 12

⇒ `w` = 12 – 9 = 3 km/h