solve an expression

Question

M motor boat heads up stream a distance if24km in a river whose current is running at3kmph. The trip up and back takes 6hours. Assuming that the motor boat maintained a constant speed, what was its speed

Comments

I dont fully understand the problem. If the boat maitain a constand speed the speed should be

24/6=4km/h But in this case what is the meaning of the river water speed?

Which one speed we re looking for? The speed to the river water or the speed to the earth?

Answer 1

Distance = rate * time (d=rt)  

Since the boat travels up and down stream the total distance is 48km.  As far as the river current, because the boat goes up and down that 3km/hr will cancel itself out.  The boat will be slowed down in one direction but spead up in the other direction

So, just use d=48, t=6 and solve for r

48=6r

r=8

8km/hr