Thread: Time to analyze Sally and John painting a house

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?

The answer is 2 hours and 24 minutes. How would one do the math to figure this out?

Originally Posted by TWN

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?

The answer is 2 hours and 24 minutes. How would one do the math to figure this out?

In 1 hour Sally paints 1/4 of a house. In 1 hour John paints 1/6 of a house. Therefore (1/4 + 1/6) = ....... of a house gets painted in 1 hour by both of them. Therefore ....

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?

The answer is 2 hours and 24 minutes. How would one do the math to figure this out?

Sally uses 4 hours (240 min) to paint a house. John uses 6 hours (360 min) to paint a house. Hence, in one min, they have painted (1/240 + 1/360) of the house. Hence, they used a total of 2 hours and 24 min (144 min) to paint the house.