SOLUTION: Jeff can mow his lawn in 4 hours time. His sister can mow the same lawn in 3 hours. How much time would it take them if they mowed it together? Could you please help with this o

Question 177862: Jeff can mow his lawn in 4 hours time. His sister can mow the same lawn in 3 hours. How much time would it take them if they mowed it together?
Could you please help with this one? Thank you.
Found 2 solutions by Mathtut, nerdybill:
Answer by Mathtut(3670) (Show Source): You can put this solution on YOUR website!
Jeff can mow 1/4 of the lawn per hour
sister can mow 1/3 of the lawn per hour
:
togethr they can mow:
(1/4)+(1/3)=(3/12)+(4/12)=7/12 of the lawn per hour
:
7/12(t)=1(job)
:
hours to mow lawn together
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
Jeff can mow his lawn in 4 hours time. Translate to:
1 lawn per 4 hours or
1/4
.
His sister can mow the same lawn in 3 hours. Translate to:
1 lawn per 3 hours or
1/3
.
Let T = time it takes for them to mow the lawn together
then
t/4 + t/3 = 1
multiplying both sides by 12:
3t + 4t = 12
7t = 12
t = 7/12 hours
or, in minutes:
t = 7/12 * 60 = 7*5 = 35 minutes

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