SOLUTION: Jack usually mows his lawn in 7 hours. Marilyn can mow the same yard in 4 hours. How much time would it take for them to mow the lawn together? (Simplify your answer. Type and int

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Question 170479: Jack usually mows his lawn in 7 hours. Marilyn can mow the same yard in 4 hours. How much time would it take for them to mow the lawn together?
(Simplify your answer. Type and integer, proper fraction, or mixed number.)
Found 2 solutions by stanbon, Mathtut:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Jack usually mows his lawn in 7 hours. Marilyn can mow the same yard in 4 hours. How much time would it take for them to mow the lawn together?
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Jack DATA:
Time = 7 hrs/job ; rate = 1/7 job/hr
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Marilyn = 4 hrs/job ; rate = 1/4 job/hr
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Together DATA:
Time = x hrs/job ; rate = 1/x job/hr
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EQUATION:
rate + rate = together rate
1/7 + 1/4 = 1/x
11/28 = 1/x
x = 28/11 = 2.545454... hrs
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Cheers,
Stan H.

Answer by Mathtut(3670) About Me  (Show Source):
You can put this solution on YOUR website!
so Jack can do 1/7 of the job per hour and Marlyn can do 1/4 of the job per hour
:
1/7(t)+1/4(t)=1(job)----->find common denominator---->28 --.so multiply by 28
:
4t+7t=28
:
11t=28
highlight%28t=28%2F11%29or 2 6/11 hours for both to mow the lawn