A person X working alone can complete a work in 5 days. A person Y completes the same amount of work in 20 days, and a person Z when working alone can complete the same amount of work in 30 days. All three people work together for 2 days but then X and Y leave. How many more days does Z need to complete the work after X and Y leave?
Choose the correct choice from the following options:
A) 13
B) 14
C) 15
D) 16
E) 17
The fraction of work completed in two days is 2/5 + 2/20 + 2/30 = 17/30   The fraction of work remaining is 1 - 17/30 = 13/30   The number of days required for Z is 13 days.   The answer is 13.
<result>A</result>
A person X working alone can complete a work in 5 days. A person Y completes the same amount of work in 20 days, and a person Z when working alone can complete the same amount of work in 30 days. All three people work together for 2 days but then X and Y leave. How many more days does Z need to complete the work after X and Y leave?