Question 177698
Sami and Marisol can mow the lawn in 40 minutes if they work together. If Marisol works twice as fast as Sami, how long does it take Sami to mow the lawn alone.
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Together DATA: 
time = 40 min/job ; rate = 1/40 job/min 
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Sami DATA:
time = 2x min/job ; rate = 1/2x job/min
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Marisol DATA:
time = x min/job ; rate = 1/x job/min
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Rate Equation:
rate + rate = together rate
1/x + 1/2x = 1/40
3x/2x^2 = 1/40
2x^2 = 120x
Divide thru by 2x to get:
x = 60 min (time it takes Marisol to do the job alone)
2x = 120 min (time it takes Sami to do the job alone)
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Cheers,
Stan H.