SOLUTION: Christopher can paint the interior of his house in 15 hours. If he hires Cynthia to help him, they can do the same job together in 9 hours. If he lets Cynthia work alone, how long

Algebra ->  Rate-of-work-word-problems -> SOLUTION: Christopher can paint the interior of his house in 15 hours. If he hires Cynthia to help him, they can do the same job together in 9 hours. If he lets Cynthia work alone, how long       Log On


   

Question 987544: Christopher can paint the interior of his house in 15 hours. If he hires Cynthia to help him, they can do the same job together in 9 hours. If he lets Cynthia work alone, how long will it take her to paint the interior of his house? Round your answer to 1 decimal place.
Start by identifying the given data.
Christopher can paint the interior of his house in 15 hours. Therefore, he can paint 1/15 of his house per hour.
Christopher and Cynthia can do the same job together in 9 hours. Therefore, they can paint 1/9 of the house per hour.
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
PAINTERS                       RATE as JOB per HOUR
Christopher                      1%2F15
Cynthia                          1%2Fx
Christopher&Cynthia              1%2F9


The rate for Christopher and Cynthia working together is the sum of their individual rates.