<PRE><B>Question 604542</B>
    lisa can sweep the paths around her home in 30 minutes. Her sister Tania takes 20 minutes to do the same job. If they work together, how long will it take to complete the job?
.
Let x = time (minutes) it takes for both
then
x(1/30 + 1/20) = 1
multiplying both sides by 60 (common denominator) we get:
x(2 + 3) = 60
x(5) = 60
x = 60/5
x = 12 minutes
</PRE>