arithmetic - a man swims some distance upstream at 12 kmhr and the same distance downstream at 20 kmhr totally in 8 hours what is the distance in one direction - skillgun

a = 20 km/hr; b = 12 km/hr,
total time = 8 hours.
.'. Average speed during two directions is 2xy/(x+y) = (2*20*12)/(20+12)
= 480/32 km/hr
Total distance in two directions = (480/32) * 8
= 120 km.
.'. Distance in one direction = 120/2 = 60 km.