SOLUTION: An engine being tested for fuel consumption was operated at two fixed settings. The first setting results in a fuel consumption of 1 gallon every 12 minutes. The second setting res

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Question 80603: An engine being tested for fuel consumption was operated at two fixed settings. The first setting results in a fuel consumption of 1 gallon every 12 minutes. The second setting results in a fuel consumption of 1 gallon every 15 minutes. The test ran 5 hours and 22 gallons of fuel were consumed. For how many minutes was the first test on the first setting?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
An engine being tested for fuel consumption was operated at two fixed settings. The first setting results in a fuel consumption of 1 gallon every 12 minutes. The second setting results in a fuel consumption of 1 gallon every 15 minutes. The test ran 5 hours and 22 gallons of fuel were consumed. For how many minutes was the first test on the first setting?
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Let "x" minutes be be running time for the 1st setting;
# of gallons consumed will be x/12
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Then "300-x" will be the running time for the 2nd setting:
# of gallons consumes will be (300-x)/15
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EQUATION:
gallons + gallons = 22
x/12 + (300-x)/15 = 22
Multiply thru by 60 to get:
5x + 1200-4x = 60*22
x=1320-1200
x=120 minutes (time the 1st setting was used)
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Cheers,
Stan H.