1.

In a stream running at 2 Kmph, a motor boat goes 10 Km upstream and back again to the starting point in 55 minutes. Find the speed of motor boat in still water?

Answer»

22 kmph



Let the speed of motor boat instill water be X kmph 

Then, speed in downstream = (X + 2) km 

and. speed in upstream = (X - 2) kmph 

Time taken to ROW 10KM & BACK = (10/X+2,10/X-2) 

10/X+2 + 10/X-2 = 55/60 

11X² - 240X - 44 = 0 

(X - 22)(11x + 2) = 0 

X = 22 or X = -2/11 

Then X = 22 kmph


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