Lisa can paint the interior of a 1000 square-foot house in 11 hours by herself. Liam can paint the same size house in 14 hours by himself. How long will it take to paint the same size house if they work together? Round your answer to the nearest hour.
A) 6 hrs
B) 12.5 hrs
C) 4 hrs
D) 8 hrs
E) none of these

Question

Quizplus · Accepted Answer

Lisa's rate is 1/11 of the house per hour, and Liam's rate is 1/14 of the house per hour. Together, they paint (1/11 + 1/14) of the house per hour. Simplifying this gives us 25/154 of the house per hour. The reciprocal of 25/154 gives the total hours needed, which is approximately 6 hours when rounded to the nearest hour.

Lisa Can Paint the Interior of a 1000 Square-Foot House