Question

In a stream that is running at 2 km/h, a man goes 10
km upstream and comes back to the starting point in
55 minutes. Find the speed of the man in still water.
(a) 20 km/h
(b) 22 km/h
(c) 24 km/h
(d) 28 km/h
​

Answer 1

Answer:

hey mate,

your answer is 22km/h

Step-by-step explanation:

Let the speed of the motor boat in still water be x kmph.

Speed downstream = (x+2) kmph

Speed upstream = (x-2) kmph

Therefore,

$\frac{10}{x - 2} + \frac{10}{x + 2} = \frac{55}{60}$

$\frac{1}{x - 2} + \frac{1}{x + 2} = \frac{55}{600} = \frac{11}{120}$

$11 {x}^{2} - 240x - 44 = 0$

(x -22)(11x + 2) = 0

x = 22

Therefore, speed of motor boat in still water = 22 kmph

hope this would help you!!