alleryA and B can do a piece of work in 10 days. B and C in 15 days. A and C in 12 days. A alone can do it in
A14 days
B16 days
C10 days
D12 days
Answer & Solution
Correct answer: B. 16 days
1/A + 1/B = 1/10.
1/B + 1/C = 1/15.
1/A + 1/C = 1/12. Sum: 2(1/A + 1/B + 1/C) = 1/10 + 1/15 + 1/12 = 6/60 + 4/60 + 5/60 = 15/60 = 1/4. So 1/A + 1/B + 1/C = 1/8. Therefore 1/A = 1/8 - 1/15 = (15-8)/120 = 7/120. A = 120/7 ≈ 17.14 days.
Hmm, options don't have 17.14. Recompute: 1/A + 1/B = 1/10 means 1/A = 1/8 - (1/B + 1/C) = 1/8 - 1/15 = (15-8)/120 = 7/120. So A ≈ 17.14. CLOSEST option = 16. BROKEN.
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