A boat travels 39 miles up the river in the same amount of time it takes to travel 51 miles down the same river. If the current is 2 miles per hour, what is the speed of the boat in still water? d r t Upstream Downstream
A)12 miles per hour
B)15 miles per hour
C)7.5 miles per hour
D)11 miles per hour
E)2 miles per hour

Question

Quizplus · Accepted Answer

Let x be the speed of the boat in still water. Then, using the formula d = rt, we can create two equations:

39 = (x-2)t
51 = (x+2)t

Since we know the time is the same in both equations, we can set them equal to each other and solve for x:

39/(x-2) = 51/(x+2)
39(x+2) = 51(x-2)
39x + 78 = 51x - 102
12x = 180
x = 15

Therefore, the speed of the boat in still water is 15 miles per hour.

A Boat Travels 39 Miles Up the River in the Same