A man rows to a place 48 kms apart and comes back in 16 hours. He finds out that he can row 6 km downstream and 4 km upstream in the same time. The speed of the stream would be-

a) 1.60 kmph

b) 3.25 kmph

c) 1.25 kmph

d) 1.80 kmph

Ans. C

Explanation – Let the time taken to move 6 km down and 4 km up be T and speed of boat be X and speed of stream be Y

Thus, speed in downstream = 6/T and speed in upstream = 4/T

Thus, 48 / (6/T) + 48 / (4/T) = 16 => T = 0.8 hours.

X + Y = 6/0.8 = 15/2    and    X – Y = 4/0.8 = 10/2  => 2Y = 5/2 => Y = 1.25 kmph