# Question #86905

Jan 27, 2018

15 kmph

#### Explanation:

Let the speed of the boat = x kmph.

In down stream in 1 hour boat goes = sp. of the boat + sp of the stream = x+3 km.

In upstream, same distance goes by 1 1/2 hours. So in 1 1/2 it travels = (sp. of the boat - sp. of the stream) x 3/2 = (x-3)3/2 km.

Hence, $\left(x - 3\right) . \frac{3}{2} = x + 3$
$\Rightarrow 3 x - 9 = 2 x + 6$
$\Rightarrow 3 x - 2 x = 6 + 9$
$\Rightarrow x = 15$