arithmetic - a boatman can row with a speed of 15 kmph in still water he finds that it takes him twice as long to row up as to row down the river find the rate of stream - skillgun

Let man’s rate against current be x kmph
Man’s rate with the current = 2x kmph
=> (1/2) (2x + x) = 15
(or) x = 10
So, man’s rate against current = 10 kmph
Man’s rate with current = 20 kmph
Rate of current = 1/2 (20 - 10) kmph
= 5 kmph