Problema Solution
Christopher can paint the interior of his house in 20 hours. If he hires Cynthia to help him, they can do the same job together in 12 hours. If he lets Cynthia work alone, how long will it take her to paint the interior of his house?
Answer provided by our tutors
In 1 hour christopher can do 1/20 work
Both can do 1/12 work
so, Cynthia alone can do 1/12-1/20 = 1/30
So can do work in 30 days