A man can row 24 kmph in still water. It takes him thrice as long to row up as to row down the river. Find the rate of the stream? Options.
A) 6  B) 12  C) 18  D) 15  E) 20
Let man's rate upsteam be X kmph   Then his rate of downstream = 3X kmph   Rate still water = 1/2 (3X + X) = 2X   2X = 24   X = 12   Rate of upstream = 12   Rate of downstream = 36   Rate of stream 1/2 ( 36 - 12) = 12 kmph   Answer is 12.
<result>B</result>
A man can row 24 kmph in still water. It takes him thrice as long to row up as to row down the river. Find the rate of the stream?