Mathematics
NULL
Medium
Question
A does a work in 30 days and B in 40 days. How many days do they need working together?
A
70 days
B
120/7 days
✓ Official correct answer
C
50 days
D
45 days
Community credibility
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A
70 days
No member explanations yet for this option.
B
120/7 days
No member explanations yet for this option.
C
50 days
No member explanations yet for this option.
D
45 days
No member explanations yet for this option.
Explanation
Combined rate = 1/30 + 1/40 = 7/120 ⇒ time = 120/7 days.