It took 3 hours to row a boat 18 km against the current. The return trip with the current took 1 1/2 hours. How do you find the speed of the rowboat in still water?
The speed is 9 km/h.
Boat speed = Vb
River speed = Vr
If it took 3 hours to cover 18km, the average speed
For the return trip, the average speed is
According to the second equation,
Substituting in the first equation: