arithmetic - a motor boat goes 10 km up streams and back again to the starting point in 55 min the current of a stream runs at the rate of 2 km per hr find the speed of the motor boat in still water - skillgun

Let the speed of boat in still water be x kmph
Speed downward = (x + 2) kmph
Speed upstream = (x – 2) kmph
Time taken to row 10 kms and back = 10/(x + 2) + 10/(x - 2) hrs
10/(x + 2) + 10/(x - 2) = 55/60 (or) 11x2 - 240x - 44 = 0
(or) 11x2 - 242x + 2x - 44 = 0 (or) (x - 22) (11x + 2) = 0
x = 22
Hence speed of motor boat in still water is 22 kmph