<PRE><B>Question 767511</B>
A motorboat travels 756 mi in 9 hours going upstream and 684 mi in 6 hours going downstream. What is the rate of the boat in still water and what is the rate of the current?
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let x=rate of speed of motorboat in still water
let c=rate of speed of current
x+c=rate of speed of motorboat downstream
x-c=rate of speed of motorboat upstream
travel time=distance/rate of speed
...
756/(x-c)=9
684/(x+c)=6
..
9x-9c=756
6x+6c=684
..
54x-54c=4536
54x+54c=6156
add
108x=10692
x=99
6c=684-6x=684-594=90
c=15
rate of speed of motorboat in still water=99 mph
rate of speed of current=15 mph
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