SOLUTION: Glenn can paint a classroom in 5 hours. His father can do it in 4 hours. How long will it take them if they work together?

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Glenn can paint a classroom in 5 hours. His father can do it in 4 hours. How long will it take them if they work together?      Log On


   

Question 909184: Glenn can paint a classroom in 5 hours. His father can do it in 4 hours. How long will it take them if they work together?
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
1/a+1/b=1/x
1/4+1/5=1/x
5/20+4/20=1/x
9/20=1/x
x=20/9 hours working together
x=2.22222222 hours working together
check
x/a+x/b=1
(20/9)/4+(20/9)/5=1
5/9+4/9=1
1.0=1
ok