A’ can swim 54 km downstream in 4.5 hours while B can swim 27 km in upstream in 5.4 hours. if the speed of A in still water is 3 times that of the speed of the stream, then find the total time taken by A to cover 21 km in upstream and time taken by B to cover 55 km in downstream (speed of stream is same for A and B).
Answers
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Given,
A can swim 54 km downstream in 4.5 hours while B can swim 27 km upstream in 5.4 hours. if the speed of A in still water is 3 times that of the speed of the stream.
To find,
The total time taken by A to cover 21 km upstream and the time taken by B to cover 55 km downstream.
Solution,
Let the speed of the stream is s and the speed of the person is u.
The downstream speed of A is,
The upstream speed of B is,
Solve equations (1) and (2) to find u and s.
After adding equations (1) and (2),
and,
Let the speed of A in still water is , the speed of B in still water be and the speed of stream for A and B is .
The speed of A is still water is,
The speed of B is still water is,
The time taken by A to cover 21 km upstream is,
The time taken by B to cover 55 km downstream is,
Thus, The time taken by A to cover 21 km upstream is 3 hours, and the time taken by B to cover 55 km downstream is .