Single correct option
A can complete a work in 12 days and B in 15 days. They work together for 2 days, after which A leaves and B, joined by C, complete the remaining work together in 3 days. If C alone can complete the whole work in x days, find x.
- A. 5 days
- B. 6 days
- C. 8 days
- D. 10 days
Show answer and solution
Answer: (B) 6 days
Rates: A = 1/12, B = 1/15 per day. Work done in first 2 days (A+B) = 2(1/12+1/15) = 2(9/60) = 18/60 = 3/10. Remaining work = 7/10. This is done by B+C in 3 days: 3(1/15 + 1/C) = 7/10 → 1/5 + 3/C = 7/10 → 3/C = 1/2 → C = 6 days.
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