SOLUTION: I am starting college again and this is a practice question on a review and I can't even remember where to begin with this. If Sally can paint a house in 4 hours, and John can pain

Question 234370: I am starting college again and this is a practice question on a review and I can't even remember where to begin with this. If Sally can paint a house in 4 hours, and John can paint the same house in 6 hour, how long will it take for both of them to paint the house together?
It does have multiple choice and they are.
A. 2 hours and 24 minutes
B. 3 hours and 12 minutes
C. 3 hours and 44 minutes
D. 4 hours and 10 minutes
E. 4 hours and 33 minutes
Thank you for your help. I haven't don't algebra in 10 years or longer. I have always done well and I think with the a little refreshing I will do better.
Answer by monika_p(71) (Show Source): You can put this solution on YOUR website!

Sally can paint a house in 4 hrs so her rate is 1/4 (1/4 of the house will be painted in one hr), and
Joh can paint house in 6 hrs , his rate is 1/6
In x hours, Sally paints x/4 of the room and John paints x/6 of the room. Since they will be working together, we will add the two parts together. The sum equals one complete job and gives us the following equation:

solving for x:
3x/12+2x/12=1
5x/12=1
5x=12
x=12/5
x=2 2/5 2hr 24mins

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