Question

A boat makes a 120-mile trip downstream in 3 hours but makes the return trip in 4 hours. What is the rate of the boat in still water? 30 mph 32 mph 35 mph

Answer 1

35mph is what I would go with...

Answer 2

Answer: 35mph

Step-by-step explanation:

The distance that the boat travels is 120 miles

Downstream the boat will have a velocity v (of the water) and the velocity of the boat V in the same direction, so the total velocity is the addition of those two.

In the return trip, the velocity of the boat is the same, but now we subtract the velocity of the water.

then we have:

V + v = 120miles/3hours = 40mph

V - v = 120miles/4hours ) = 30mph

Now we have two equations and two values that we want to find, the first step is isolate v in one of the two equations, let's choose the second:

V - v = 30mph

v = V - 30mph

Now, we can replace this in the first equation:

V + v = 40mph

V + V - 30mph = 40mph

2*V = 70mph

V = 35mph

The velocity of the boat in still water will be 35mph