SOLUTION: Sam can paint the classroom in 5 hours and working with Sal they can paint the room in 3 hours. How long does it take sal to paint the room alone?

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Question 1030798: Sam can paint the classroom in 5 hours and working with Sal they can paint the room in 3 hours. How long does it take sal to paint the room alone?
Answer by ikleyn(52790) About Me  (Show Source):
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Sam can paint the classroom in 5 hours and working with Sal they can paint the room in 3 hours. How long does it take Sal to paint the room alone?
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Sam's rate of work is  1%2F5  of the room painted surface per hour.

Sams and Sal's combined rate of work is  1%2F3  of the room area per hour when they work together.

Hence, Sal's rate of work is the difference

1%2F3+-+1%2F5 = 5%2F15+-+3%2F15 = 2%2F15 of the room area per hour.

It means that Sal takes 15%2F2 = 71%2F2 hours to pint the room working alone.

For many other similar problems on joint work, you can find their detailed solutions in these lessons
    - Using Fractions to solve word problems on joint work
    - Solving more complicated word problems on joint work
in this site.