<PRE><B>Question 275932</B>
DON CLEAN THE HOUSE IN 3 HOURS. LISA CLEANED IT IN 8 HOURS.
 HOW LONG WILL IT TAKE THEM TO CLEAN THE HOUSE TOGETHER?
:
Let t = time required working together
:
Let the completed job = 1 (a clean house)
:
Each will do a fraction of the job, the two fractions add up to 1
{{{t/3}}} + {{{t/8}}} = 1
Multiply the equation by 24 to clear the denominators, results
8t + 3t = 24(1)
11t = 24
t = {{{24/11}}
t = 2{{{2/11}}} hrs
or
2 hrs + ({{{2/11}}}*60) ~ 11 min</PRE>