A can complete a project in 20 days and B can complete the same project in 30 days. If A and B start working on the project together and A quits 10 days before the project is completed, in how many days will the project be completed? Pick:
A) 18 days
B) 27 days
C) 26.67 days
D) 16 days
E) 12 days
Answer   A can complete a project in 20 days. So, A will complete 1/20th of the project in a day.   B can complete a project in 30 days. So, B will complete 1/30th of the project in a day.   Let the total number of days taken to complete the project be x days.   B worked for all x days. However, A worked for (x - 10) days because A quits 10 days before the project is completed.   In a day, A completes 1/20th of the project.   Therefore, A would have completed x−10/20th of the project in (x - 10) days.   In a day, B completes130130th of the project.   Therefore, B would have completed x/30h of the project in x days.   ∴ x−10/20+x/30= 1   Or x = 18.   Choice 18 days
<result>A</result>
A can complete a project in 20 days and B can complete the same project in 30 days. If A and B start working on the project together and A quits 10 days before the project is completed, in how many days will the project be completed?