Mathematics
NULL
Medium
Question
P and Q finish a work in 20 and 12 days. P starts alone; Q joins after 4 days until the end. How long does the work last?
A
5 days
B
10 days
✓ Official correct answer
C
15 days
D
12 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
5 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
12 days
No member explanations yet for this option.
Explanation
P alone for 4 days does 1/5. Remaining 4/5 at combined rate 1/20 + 1/12 = 2/15 needs 6 days. Total = 10 days.