A motorboat that travels with a speed of 20 km/hour in still water has traveled 20 km against the current and 180 km with the current, having spent 8 hours on the entire trip. Find the speed of the current of the river.

Answer 1

speed of the curren --- x km/h
so the speed with the current = 20+x km/h
and speed against the current = 20 - x km/h

time against the current = 20/(20-x)
time with the current = 180/(20+x)

20/(20-x) + 180/(20+x) = 8

solve for x, you will get a quadratic equation