Question

A motorboat goes downstream in a river and covers the distance between two coastal towns in 5 hours it covers this distance upstream in 6 hours if the speed of the stream is 3 kilometre per hour find the speed of the boat in still water

Answer 1

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

Given that the speed of the stream=3km/h.

Upstream

Speed = ( x - 3)km/h

Distance = Speed x Time

Distance = 6 (x - 3)km


Downstream

Speed = ( x + 3)km/h

Distance = Speed x Time

Distance = 5(x + 3)km

Now Solve for x

Since both the distance are the same

6(x- 3)= 5( x + 3)

6x - 18= 5x + 15

x = 33 km/h