SOLUTION: The officejet printer can copy Janet's dissertation in 20 min. The laserjet printer can copy the same document in 12 min. If the two machines work together, how long would they tak

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Question 681971: The officejet printer can copy Janet's dissertation in 20 min. The laserjet printer can copy the same document in 12 min. If the two machines work together, how long would they take to copy the dissertation?
Answer by stanbon(75887) About Me  (Show Source):
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The officejet printer can copy Janet's dissertation in 20 min. The laserjet printer can copy the same document in 12 min. If the two machines work together, how long would they take to copy the dissertation?
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Officejet rate: 1/20 job/min
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Laserjet rate: 1/12 job/min
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Togeterh rate = 1/x job/min
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Equation:
rate + rate = together rate
1/20 + 1/12 = 1/x
12x + 20x = 12*20
32x = 240
x = 7.5 min (time to do the job together)
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Cheers,
Stan H.