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| Math Central | Quandaries & Queries |
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Question from Mohanad, a student: Howie Sorkin can travel 8 miles upstream in the same time it takes him to go 12 miles downstream. His boat goes 15 mph in still water. What is the rate of the current? |
Hi,
The key to this problem is that
$\mbox{ distance} = \mbox{ time} \times \mbox{ rate.}$
You have two equations, one from going upstream and the other for going downstream. The time is the same for each equation and the distances are 8 and 12 miles.
Suppose that the rate of the current is $r$ miles per hour then the boat travels downstream at $r + 15$ miles per hour. What is the speed of the boat when travelling upstream? Solve for $r.$
Penny
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