arithmetic - a boat takes 4 hours for travelling downstream from point a to point b and coming back to point a upstream if the velocity of the stream is 2 kmph and the speed of the boat in still water is 4 kmph what is the distance between a and b - skillgun

Let the distance between A and B be x km.
Speed downstream = 6 kmph, speed upstream = 2 kmph.
=> (x/6) + (x/2) = 4
=> 4x = 24
hence x = 6
Distance AB = 6 km