Question

The speed of the boat in still water is 11km /hr it goes 12km upstream and return downstream in 2hrs 45mins find the speed of the stream

Answer 1

Let the speed of the stream be "x km/ hr.".

Speed of boat in still water = 11 km/ hr.

Therefore, speed of boat upstream = 11 - x

speed of boat downstream = 11 + x

A.T.Q., 12 / 11 - x + 12 / 11 + x = 2 3/4

===> 12 ( 1/ 11 -x + 1/ 11 + x ) = 11 / 4

===> 22 / 121 - x2 = 11 / 4*12

===> 22/ 121 - x2 = 11 / 48

===> 1331 - 11 x2 = 1056

===> 11 x2 = 275

===> x2 = 25

===> x = +5 or -5

As speed can't be negative, x not equal to -5.