Question 717717
the speed of a current is 4 mph. if a boat travels 75 miles down stream in the same time it takes to travel 39 miles up stream, what is the speed of the boat in still water
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let x=speed of the boat in still water
x+4=speed of the boat downstream
x-4=speed of the boat upstream
travel time=distance/speed
..
75/(x+4)=39/(x-4)
75x-300=39x+156
36x=456
x=12.67 (rounded)
speed of the boat in still water=12.67 mph