SOLUTION: Joe can paint his house by himself in 4 days. His wife needs an additional day to complete the job if she works by herself. If they work together, find how long it takes to paint

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Question 726924: Joe can paint his house by himself in 4 days. His wife needs an additional day to complete the job if
she works by herself. If they work together, find how long it takes to paint the house.
Please show me the answer I came up with 2.50 days. I want a professional answer please.
Answer by josgarithmetic(39630) About Me  (Show Source):
You can put this solution on YOUR website!
Think according to rates as jobs per day. When persons do the work simultaneously, their rates are additive.

Person_______________rate in jobs per day
Joe__________________1%2F4________________
His Wife_____________1%2F%284%2B1%29____________
Joe+Wife_____________1%2F4%2B1%2F5___________

All that is necessary to to compute the sum of the rates of Joe and his wife. Note how 1%2F%284%2B1%29 is the same as 1%2F5.