arithmetic - a boat covers a certain distance downstream in 4 hours while it comes back in 6 hours if the speed of the stream be 2 kmph what is the speed of the boat in still water - skillgun

Let the speed of the boat in still water be x kmph. Then,
Speed downstream = (x+2) kmph; speed downstream = (x -2) kmph.
.'. (x+2)4 = (x-2)6
=> 2x = 20
=> x = 10 kmph.