SOLUTION: A speedboat takes 4 hours longer to go 80 miles up a river than to return. If the boat cruises at 15 miles per hour in still water, what is the rate of the current?
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Question 387781: A speedboat takes 4 hours longer to go 80 miles up a river than to return. If the boat cruises at 15 miles per hour in still water, what is the rate of the current?
You can put this solution on YOUR website! Let c = rate of the current.
Then 15+c = rate of speedboat down the river
15 - c = rate of speedboat up the river
From the Formula D = R*T, we get T = D/R, so = time of speedboat up the river = time of speedboat down the river. From these we get , or .
Combining and simplifying, we get , or , or (c-5)(c+45) = 0.
Hence c = 5 miles per hour, the rate of the current.
