Question

A boy can row a boat 63 km upstream in seven hours and 132 km downstream in 12 hours. What is the rate of flow of the river?​

Answer 1

Answer:

6

Step-by-step explanation:

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Answer 2

Given,

Distance covered upstream = 63 km

Time is taken in upstream = 7 hours

Distance covered downstream = 132 km

Time is taken in downstream = 12 hours

To find,

We have to find the rate of flow of the river.

Solution,

The rate of flow of the river is 9 km/hr in upstream and 11 km/hr in downstream.

Let the speed of a boy in still water be x km/hr

Speed of the current water = y km/hr

Speed in upstream = (x-y) km/hr

Speed in downstream = (x+y) km/hr

Now, Time = Distance/ Speed

In upstream,

                         7= 63/(x-y)    

                        x-y = 9         (1)

In downstream,

                        12 = 132/(x+y)

                       x + y = 11       (2)

Adding equation(1) and (2), we get,

                         2x = 20

                          x = 10

Substituting the value of x in equation (1), we get,

                        y = 11-10

                       y = 1

So, the speed of a boy in still water is 10 km/hr and, the speed of the current water is 1 km/hr.

Hence, the rate of flow of the river is 9 km/hr upstream and 11 km/hr downstream.