SOLUTION: A boat moves 9 kilometers upstream in the same amount of time it moves 15 kilometers downstream. If the rate of the current is 8 kilometers per hour, find the rate of the boat in s

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Question 964854: A boat moves 9 kilometers upstream in the same amount of time it moves 15 kilometers downstream. If the rate of the current is 8 kilometers per hour, find the rate of the boat in still water.
Answer by macston(5194) About Me  (Show Source):
You can put this solution on YOUR website!
r=rate in still water
15km%2F%28r%2B8km%2Fhr%29=9km%2F%28r-8km%2Fhr%29 Cross multiply.
Subtract 9rkm from each side.
6rkm-120km%5E2%2Fhr=72km%5E2%2Fhr Add 120km^2/hr to each side.
6rkm=192km%5E2%2Fhr Divide each side by 6km.
r=32km%2Fhr
ANSWER: The rate of the boat in still water is 32 km/hr.
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CHECK:
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15km%2F%2832km%2Fhr%2B8km%2Fhr%29=9km%2F%2832km%2Fhr-8km%2Fhr%29
15km%2F%2840km%2Fhr%29=9km%2F%2824km%2Fhr%29
0.375hr=0.375hr