SOLUTION: Julie and Eric row their boat( at a constant speed) 45 miles downstream for 5 hours, helped by the current. Rowing at the same rate, the trip back against the current takes 9 hours

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Question 167202: Julie and Eric row their boat( at a constant speed) 45 miles downstream for 5 hours, helped by the current. Rowing at the same rate, the trip back against the current takes 9 hours. Find the rate of the current.
Answer by Mathtut(3670) About Me  (Show Source):
You can put this solution on YOUR website!
d=r*t in this instance r%5Bd%5D=r%5Bb%5D%2Br%5Bc%5D r%5Bu%5D=r%5Bb%5D-r%5Bc%5D where r%5Bd%5Drate downstream and r%5Bu%5D rate upstream r%5Bb%5Drate of the boat r%5Bc%5D is the rate of the current r%5Bd%5D=45%2F5=9

we know that 45=r%5Bd%5D%285%29---->45=%28r%5Bb%5D%2Br%5Bc%5D%295
: 45=r%5Bu%5D%289%29---->45=%28r%5Bb%5D-r%5Bc%5D%299
45=5r%5Bb%5D%2B5r%5Bc%5D
45=9r%5Bb%5D-9r%5Bc%5D
multiply top by 9 and bottom by 5 to eliminate the r%5Bc%5Dterms
90r%5Bb%5D=630 highlight%28r%5Bb%5D=7%29
so highlight%28r%5Bc%5D=9-7=2%29