Question

In a fixed time , a boy swims double the distance along the current that he swims against the current. If the speed of the current is 3 km/ hr , the speed of the boys in still water is


a. 6 km / hr


b. 9 km / hr


c. 10 km/ hr


d. 12 km / hr

Answer 1

The answer is option "a" . 6 km/h.

Answer 2

Explanation:

Let the rate of swimming in still water be p kmph

∴ Rate down-stream = (p + 3) kmph

∴ Rate up-stream = (p – 3) kmph

According to the question,

(p + 3) t = 2 (p – 3) × t

⇒ p + 3 = 2p – 6

⇒ p = 9 kmph

Using the given formula :

Here, t1 = 2k , t2 = k

Speed of Stream = 3 km/hr

∴

Speed of Boy

=

t1 + t2

Speed of Stream t1 - t2

Speed of Boy

=

2k + k

3 2k - k

Speed of Boy = 9 km/hr