Math
posted by Britanny on .
If sally can paint a house in 4 hours and John can paint the same house in 6 hours. How long will it take for them to paint the house together?

HINT
Sally can paint 3 houses in 12 hours.
John can paint 2 houses in 12 hours.
Therefore, Sally and John together can paint 5 houses in 12 hours.
So, at the same rate, how long will it take them to paint 1 house together? 
Would you please further explain? I'm lost.

Use Leo's hint that together they could paint 5 houses in 12 hours.
Divide: 12 by 5 = 2.4
That means that Sally and John together can paint a house in 2.4 hours. 
or..
Sally's rate = house/4 hrs
John's rate = house/6 hours
combined rate = house/4 + house/6 = 5house/12
so time with combined rate = house/(5house/12) = 12/5 = 2.4 hours 
How did you come up with the combine rate of house/4 + house/6 = 5houses/12?

house/4 + house/6
= house(1/4 + 1/6)
= house(5/12)
= 5house/12
house is just my name for the constant, you could call it anything you want, say x or y or a or b ....
in the end it cancels 
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