<PRE><B>Question 177862</B>
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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