SOLUTION: You can paint a certain room in 7 hours. Your brother can do it in 4 hours. How long does it take the two of you working together?

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Question 648334: You can paint a certain room in 7 hours. Your brother can do it in 4 hours. How long does it take the two of you working together?

Answer by checkley79(3341) About Me  (Show Source):
You can put this solution on YOUR website!
1/7+1/4=1/X Find a common denominator (7*4=28)
4/28+7/28=1/x
11/28=1/x Cross multiply
11x=28*1
11x=28
x=28/11
x=2.55 Hours when they work together.
Proof:
1/7+1/4=1/2.55
.143+.25=.392
.393=.392