SOLUTION: It takes Sal 5 hours to paint a house. It takes Mary 3 hours to paint the same house. How long will it take to paint the house if both of them work together?

Question 38089: It takes Sal 5 hours to paint a house. It takes Mary 3 hours to paint the same house. How long will it take to paint the house if both of them work together?
Answer by junior403(76) (Show Source): You can put this solution on YOUR website!
It takes Sal 5 hours to paint a house. It takes Mary 3 hours to paint the same house. How long will it take to paint the house if both of them work together?
Let x = the time it would take the two to work together.
If Sal can do the job in 5 hrs. then in one hour he can do 1/5 of the job.
If Mary can do the job in 3 hrs. then in one hour he can do 1/3 of the job.
So together, if it takes x hours to do the entire job we show that as...
1/5x + 1/3x = 1 complete job.
Find LCD = 15
15(1/5x + 1/3x) = 15(1)
Multiply...
3x + 5x = 15
Add like terms...
8x = 15
Divide by 8...
x = 15/8
or 1 7/8 hrs.
Sal and Mary can do the job together in just under 2 hrs.
Good Luck!
Thanks for the question!

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