Question 1032406
Similar problem.
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A boat can travel 39 mph in still water.If it travels 235 miles with the current in the same length of time it travels 155 miles against the current, what is the speed of the current? 
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Time upstream = 155/(39 - c)
Time downstream = 235/(39+c)
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155/(39 - c) = 235/(39+c)
31/(39 - c) = 47/(39+c)
31*(39 + c) = 47*(39 - c) 
etc