Choose the one alternative that best completes the statement or answers the question.

Solve the problem.
-A boat can go 136 mph in still water. It takes as long to go 720 mi upstream as it does to go downstream 810 mi. How fast is the current?
A) 7 mph
B) 9 mph
C) 8 mph
D) 1 mph

Question

Choose the one alternative that best completes the statement or answers the question. 
 
Solve the problem.
-A boat can go 136 mph in still water. It takes as long to go 720 mi upstream as it does to go downstream 810 mi. How fast is the current?
A) 7 mph
B) 9 mph
C) 8 mph
D) 1 mph

Quizplus · Accepted Answer

The speed of the current can be found by setting up equations based on the distance = speed × time formula for both upstream and downstream. Let the speed of the current be $c$ mph. The speed of the boat upstream is $136 - c$ mph, and downstream is $136 + c$ mph. Since the time taken is the same for both trips, we can set up the equation $\frac{720}{136 - c} = \frac{810}{136 + c}$. Solving this equation for $c$ gives $c = 8$ mph.

Choose the One Alternative That Best Completes the Statement or Answers