Question 83746This question is from textbook college algebra & trigonometry
: My first problem is out of the text book:
an inlet pipe can fill Reynaldo's pool in 5hr, while an outlet pipe can empty it in 8hr. In his haste to surf the Internet, Reynaldo left both pepies open. How long did it take to fill the pool.
The second question is the speed of a stream is 4mph. A boat travels 10 miles upstream in the same time it takes to travel 18 miles downstream. what is the speed of the boat in still water?
This question is from textbook college algebra & trigonometry
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! an inlet pipe can fill Reynaldo's pool in 5hr, while an outlet pipe can empty it in 8hr. In his haste to surf the Internet, Reynaldo left both pepies open. How long did it take to fill the pool.
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Filling Pipe DATA:
Time = 5 hr/job ; Rate = (1/5) job/hr.
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Emptying Pipe DATA:
Time = 8 hr/job ; Rate = (1/8) job/hr.
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Working Together DATA:
Time = x hr/job ; Rate = 1/x job/hr
Also Together Rate = 1/5-1/8 = 3/40 job/hr
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EQUATION:
1/x = 3/40
x= 40/3 = 13 1/3 hrs. (Time it will take to fill the pool.)
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The second question is the speed of a stream is 4mph. A boat travels 10 miles upstream in the same time it takes to travel 18 miles downstream. what is the speed of the boat in still water (let be "b") ?
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Upstream DATA:
Distance = 10 mi ; Rate = b-4 mph ; time = d/r = 10/(b-4) hrs.
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Dosnstream DATA:
Distance = 18 mi ; Rate = b+4 ; time = d/r = 18/(b+4)
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EQUATION:
time up = time down
10/(b-4) = 18/(b+4)
10b+40 = 18b-72
-8b = -112
b= 14 mph ( this is the speed of the boat in still water)
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Cheers,
Stan H.
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