A man can row 34/3 kmph in still water and finds that it takes him thrice as much time to row up than as to row down the same distance in the river. The speed of the current is:

Let speed upstream be x kmph
Then speed downstream = 3x kmph
Speed in still water = (1/2)​(3x + x)kmph
=2x kmph

Now
2x = 34/3
x = (34/3) × 2
x = 17/3

So Speed upstream = 17/3 km/hr
Speed downstream = 17 km/hr

Hence speed of the current =(1/2){17 - (17/3)} km/hr.
= (1/2)(51 - 17)/3 km/hr.
= (1/2)(34/3) km/hr.
= 17/3 km/hr.