Posted by **Katie** on Monday, March 5, 2007 at 9:51am.

If Sally can paint a house in 4 hours, & John can paint the same house in 6 hours, how long will it take for both of them to paint the house together? '

I am having trouble remembering how to set up the equation?

Amount of work accomplished =

(Rate of work) x time

The rates of work are measured in houses per hour, and can be added for the two workers. Sally's rate is 1/4 house per hour. John's rate is 1/6 house per hour.

1 house = (1/6 + 1/4)* Time

Time = 1/(1/6 + 1/4) = 1/(2/12 + 3/12)

= 1/(5/12) = 12/5 hour = 2 2/5 hr

That is two hours and 24 minutes

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