# It takes John 20 hours to paint a building. It takes Sam 15 hours to paint the same building. How long will it take for them to paint the building if they work together, with Sam starting one hour later than John?

##### 1 Answer

Oct 31, 2017

#### Explanation:

Let the total amount of work to paint 1 building be

Let the work rate per hour for John be

Let the work rate per hour for Sam be

Known: John takes 20 hours on his own

Known: Sam takes 15 hours on his own

Let the time in hours be

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Putting all of this together we start with:

but

Divide both sides by