SOLUTION: Can you help me with this problem? Jill and Sarah are mowing a lawn together (with separate mowers). It will take them 2 1/2 hours to complete. If Jill (by herself) can mow the sam

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Question 755495: Can you help me with this problem? Jill and Sarah are mowing a lawn together (with separate mowers). It will take them 2 1/2 hours to complete. If Jill (by herself) can mow the same lawn in 4 hours, how long would it take Sarah to mow the lawn by herself?
Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website!
Jill and Sarah are mowing a lawn together (with separate mowers). It will take them 2 1/2 hours to complete. If Jill (by herself) can mow the same lawn in 4 hours, how long would it take Sarah to mow the lawn by herself?
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Together DATA: time = 5/2 hrs/job ; rate = 2/5 job/hr
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Jill DATA::::: time = 4 hrs/job ; rate = 1/4 job/hr
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Sarah DATA:::: time = x hrs/job ; rate = 1/x job/hr
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Equation:
rate + rate = together rate
1/x + 1/4 = 2/5
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Multiply thru by 20x to get:
20 + 5x = 8x
3x = 20
x = 20/3 = 6 2/3 hrs (time for Sarah to do the job alone)
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Cheers,
Stan H.
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