SOLUTION: I would love some help with this problem. Jack can mow a lawn in 3 hours. Marilyn can mow the same lawn in 4 hours. How much time will it take if they do it together? Than

Question 251745: I would love some help with this problem.
Jack can mow a lawn in 3 hours. Marilyn can mow the same lawn in 4 hours. How much time will it take if they do it together?

Thank you so much for any help!!!
Found 2 solutions by edjones, stanbon:
Answer by edjones(8007) (Show Source): You can put this solution on YOUR website!
Jack does 1/3 the job in 1 hr; Marilyn 1/4 in 1 hr.
1/3 + 1/4
=4/12 + 3/12
=7/12 of the job in 1 hr together
Or 12/7 hrs to do the job together.
.
Ed
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Jack can mow a lawn in 3 hours. Marilyn can mow the same lawn in 4 hours. How much time will it take if they do it together?
------------
Jack rate = 1/3 job/hr
Marilyn rate = 1/4 job/hr
Together rate = 1/x job/hr
----------------------------
Equation:
rate + rate + together rate
1/3 + 1/4 = 1/x
Multiply thru by 12x
4x + 3x = 12
7x = 12
x = 12/7 = 1 5/12 hrs (time needed for the job if they work together)
x = 1 hr 25 minutes
========================
Cheers,
Stan H.
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