SOLUTION: a father and a son working together can finish painting a room in 6 hours. working alone, the father takes 9 hours to do the painting. how many painting hours will it take the son,

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Question 885705: a father and a son working together can finish painting a room in 6 hours. working alone, the father takes 9 hours to do the painting. how many painting hours will it take the son, working alone to finish the painting room?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Add their rates of painting to get their
rate painting together
Let +t+ = time in hours for son to paint
the room working alone
----------------------------
( 1 room ) / ( 9 hrs ) + ( 1 room ) / ( t hrs ) = ( 1 room ) / ( 6 hrs )
+1%2F9+%2B+1%2Ft+=+1%2F6+
Multiply both sides by +54t+
+6t+%2B+54+=+9t+
+3t+=+54+
+t+=+18+
It takes the son 18 hours working alone to paint the room
------------------
check:
+1%2F9+%2B+1%2Ft+=+1%2F6+
+1%2F9+%2B+1%2F18+=+1%2F6+
+2%2F18+%2B+1%2F18+=+3%2F18+
+3%2F18+=+3%2F18+
OK