A boat can travel 53⁢mph in still water. If it travels 360 miles with the current in the same length of time it travels 276 miles against the current, what is the speed of the current?

Question

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Answer 1

Time=distance÷speed. The effective speed with the current is 53+x and against the current is 53-x where x is the speed of the current, so 360/(53+x)=276/(53-x).

360(53-x)=276(53+x), 360×53-360x=276×53+276x, 636x=360×53-276×53=53(360-276)=53×84.

x=53×84/636=84/12=7mph.