Amotorboat travels 256km in 5 hourse going upstream. it travels 385 km going downstream in the same amount of time. what is the rate of the boat in still water and what is the rate of the current?

Velocity upstream = 265/5 =53 km/h
Velocity downstream = 385/5 77 km/h
Notice that when the boat was going upstream her speed was reduced due to the velocity of the stream;
The real velocity in still water is:
V(REAL)  = 53 + V(stream) and
V(REAL)  = 77 - V(stream)

Then the average  =(53+V + 77 - v)/2 = 130/2 = 65km/h