<PRE><B>Question 339137</B>
Lisa can shovel snow from her driveway in 35 minutes. Tom can do the same job in 55 minutes. How long would it take Lisa and Tom to shovel the driveway if they worked together? 
.
Let x = minutes if they worked together
then
x(1/35 + 1/55) = 1
Multiplying both sides by 35*55:
x(55 + 35) = 35*55
x(90) = 35*55
x = 1925/90
x = 21.39 minutes

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