SOLUTION: Joe can paint a room in 3 hours, fred can paint a room in 4 hours and Bill can paint a room in 6 hours. How long does it take them to paint a room togther?

Algebra ->  Rate-of-work-word-problems -> SOLUTION: Joe can paint a room in 3 hours, fred can paint a room in 4 hours and Bill can paint a room in 6 hours. How long does it take them to paint a room togther?      Log On


   

Question 785797: Joe can paint a room in 3 hours, fred can paint a room in 4 hours and Bill can paint a room in 6 hours. How long does it take them to paint a room togther?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Add their rates of painting to get the
rate of all 3painting together
( 1 room )/( 3 hrs ) + ( 1 room )/( 4 hrs ) + ( 1 room )/( 6 hrs )
= ( 1 room )/( t hrs )
--------------------------
+1%2F3+%2B+1%2F4+%2B+1%2F6+=+1%2Ft+
Multiply both sides by +12t+
+4t+%2B+3t+%2B+2t+=+12+
+9t+=+12+
+t+=+4%2F3+
+4%2F3+=+1+%2B+1%2F3+
+%281%2F3%29%2A60+=+20+
It takes them 1 hr and 20 min to paint
the room together