A can do a piece of work in 10 days and B in 20 days. They work together but 2 days before the completion of the work A leaves. In how many days remaining work will be completed by B? A किसी काम को 10 दिन में करता है और B 20 दिन में करता है। दोनों साथ साथ काम शुरू करते है और काम पूरा होने से दो दिन पहले A काम छोड़ देता है। शेष काम को B कितने दिनों में पूरा करेगा?
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6 day/दिन
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8 day/दिन
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4 day/दिन
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12 day/दिन
B
Correct answer
Explanation
A's rate = 1/10 work/day, B's rate = 1/20 work/day. Combined rate = 3/20 work/day. If A leaves 2 days before completion, they worked together for (total-2) days. Work done together = (3/20)(total-2). Remaining work = 1 - (3/20)(total-2) = (20 - 3total + 6)/20. B alone does 1/20 per day, so B's days = 20 - 3total + 6. Also total work = (3/20)(total-2) + (1/20)×2 = 1. Solving: total = 10 days. B works alone for 2 days = 8 days.