A, B and C can do a piece of work in 10, 12 and 15 days respectively. A leaves 5 days before the completion of the work and B leaves 2 days after A. In how many days the whole work lasts for? A, B और C एक काम को क्रमशः 10, 12 और 15 दिनों में कर सकते हैं | A काम समाप्त होने से 5 दिन पहले काम छोड़ देता है और B, A के 2 दिन बाद काम छोड़ देता है| पूरा कार्य कितने दिन तक चला ?
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6 days/दिन
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12 days/दिन
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13 days/दिन
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7 days/दिन
D
Correct answer
Explanation
Let total work = 60 days. A works for 2 days (2/60), B works for 4 days (4/60), and C works for all 7 days (7/60). Total work = 2/60 + 4/60 + 7/60 = 13/60 of total work per day. To complete 60 units of work: C's full contribution (7/60 × 7 = 49/60) plus A and B's partial work (2/60 + 4/60 = 6/60) gives 55/60. More precisely: Let total days = d. A works for d-5 days, B works for d-3 days, C works for d days. Solving (d-5)/6 + (d-3)/5 + d/4 = 1 gives d = 7.