Mathematics
NULL
Medium
Question
A and B separately take 9 and 12 days. They work alternately with A starting first. How many days to finish the work?
A
42/4 days
B
41/4 days
✓ Official correct answer
C
55 days
D
None of these
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
42/4 days
No member explanations yet for this option.
B
41/4 days
No member explanations yet for this option.
C
55 days
No member explanations yet for this option.
D
None of these
No member explanations yet for this option.
Explanation
Each 2-day cycle does 1/9 + 1/12 = 7/36. After 5 cycles (10 days): 35/36 left. A needs (1/36)/(1/9) = 1/4 day more ⇒ total = 41/4 days.