arithmetic - a man rows at 10 kmph in still water he goes to a place 96 km away and come back taking 20 hours totally what is the speed of current - skillgun

Let the speed of current be x kmph.
Upstream = (10-x) kmph; downstream = (10+x) kmph
Total time = distance covered in both up and down streams
20 = 96/(10-x) + 90/(10+x)
=> 96(10+x+10-x) = 20(10-x)(10+x)
=> 96*20 = 20*(x^2 - 10^2)
x^2 = 100-96 => x = 2 kmph.