posted by Katie on .
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