Question

A boat makes a 120-mile trip downstream in 3 hours but makes the return trip in 4 hours. If b = the rate of the boat in still water and c = the rate of the current, which of the following equations represents the trip downstream?
3(b - c) = 120
3(b + c) = 120
4(b + c) = 120

Answer 1

I think C will be the answer

Answer 2

The rate downstream = b + c because the water and boat are moving in same direction.

also time downstream = 3 hours

 time * rate = distance 

3 * (b + c)  = 120


so its the second choice.