Mathematics
NULL
Medium
Question
X and Y finish a work in 20 and 12 days. X works alone for 4 days, then Y joins until the end. How long does the work last?
A
6 days
B
10 days
✓ Official correct answer
C
15 days
D
20 days
Community credibility
Registered members can vote for the answer they believe is correct today and explain why. If the facts change after an election or news event, suggest a new option so others can vote it up.
A
6 days
No member explanations yet for this option.
B
10 days
No member explanations yet for this option.
C
15 days
No member explanations yet for this option.
D
20 days
No member explanations yet for this option.
Explanation
X alone does 4/20 = 1/5. Remaining 4/5 at 1/20 + 1/12 = 2/15 per day needs 6 days. Total = 10 days.