Anew crew of painters can paint a small apartment in 12 hours. an experienced crew can paint the small apartment in 6 hours. how many hours does it take to paont the apartment when the two crews work together?

If both crews work together, let's say the finish the job in "t" hours.

so.. in 1 hour, they have done 1/t of the whole work.

now, the new crew, working by itself can do the whole job in 12 hours, that means, in 1 hour, they have done only 1/12 of all the work.

the experienced crew, can do the job in 6 hours, that means in 1 hour, they have done 1/6 of all the work.

now, let's add their rates for 1 hour worth, to see what we get.



and pretty sure you know how much that is.