Question 393275
If sally can paint a house in 4 hours, and John can paint the same house in 6 hours, how long will it take for both of them to paint the house together? 
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Sally DATA:
time = 4 hrs/job ; rate = 1/4 job/hr
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John DATA:
time = 6 hrs/job ; rate = 1/6 job/hr
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Together DATA:
time = x hrs/job ; rate = 1/x job/hr
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Equation to solve for "x":
rate + rate = together rate
1/4 + 1/6 = 1/x
Multiply thru by 12x to get:
3x + 2x = 12
5x = 12
x = 12/5 = 2.8 hrs (time to do the job when they work together)
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Note: 2.8 hrs = 2 hr + 0.8*60min = 2hr+48 minutes
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Cheers,
Stan H.