Question

A sailor goes 8km downstream in 40 minutes and returns in 1hr.
Determine the speed of the sailor in still water and speed of the current.





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Answer 1

Let the speed of sailor in still water be x km/hr and the speed of stream be y km/hr.

The speed of boat (upstream) = (x - y) km/hr.

The speed of boat (downstream) = (x + y) km/hr.

Now,

A.T.Q.

(1) 8 / x + y = 40 / 60 (Since, Time = Distance / Speed)

===> x + y = 12 ----------------- (1)

(2) 8/ x - y = 1 (Since, Time = Distance / Speed)

===> x - y = 8 ------------------- (2)

On adding (1) and (2),

===> x + y + x - y = 12 + 8

===> 2 x = 20

===> x = 10

By (1),

===> 10 + y = 12

===> y = 2

Ans :- The speed of sailor in still water is 10 km / hr.

The speed of stream is 2 km / hr.