SOLUTION: A motorboat takes 5 hours to travel 150mi going upstream. The return trip takes 3 hours going downstream. What is the rate of the boat in still water and what is the ra

Let x=rate of boat in still water
let c=rate of current


Then (x+c) is the rate of boat downstream
     (x-c) is the rate of boat upstream

rate = 

Rate upstream    x-c = .
Rate downstream  x+c = .


Simplify:

x - c = 30     (1)
x + c = 50     (2)


Add the equations (1) and (2). You will get

2x = 30 + 50 = 80  ====>  x =  = 40.


Answer.  Rate of the boat in still water = 40 mph.

         Rate of current = 10 mph.