'A' takes twice as much time as 'B' to complete a work, and 'C' does it in the same time as both 'A' and 'B' together. If all three work together and complete the work in 5 days, then the time taken by 'B' to complete the work alone is:
A12 days
B14 days
C15 days ✓ Correct
D18 days
Correct answer: (C) 15 days
Explanation
B alone takes 15 days.
Let B take b days, then A takes 2b days.
C equals A and B together: rate 1/2b + 1/b = 3/2b.
All three rate = 1/2b + 1/b + 3/2b = 3/b.
3/b = 1/5, so b = 15 days.
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