Q

# The current of stream runs at 1 kmph. A motor boat goes 35 km up stream and back again to the start

The current of stream runs at 1 kmph. A motor boat goes 35 km up stream and back again to the starting point in 12 hours. The speed of the motor boat is?

• Option 1)

6 kmph

• Option 2)

5.5 kmph

• Option 3)

9 kmph

• Option 4)

8.5 kmph

• Option 5)

7 kmph

Views

Let's assume the speed of motorboat is x.

Stream Speed = 1

Upstream Speed = x-1

Downstream Speed = x+1

According to question,

$\frac{35}{x+1}+\frac{35}{x-1} = 12$

$\frac{35x - 35 + 35x + 35}{x^{^2}-1}= 12$

$70x = 12x^{2}-12$

$12x^{2}-70x-12 = 0$

$x=6, -1/6$