Q. A can do a piece of work in 20 days and B can do the same piece of work in 30 days. Find that in how many days both can do the work?
Answer: 12 days
Notes: A's 1 day's work $latex = \frac{1}{20}&s=1$ B's 1 day's work $latex = \frac{1}{30}&s=1$ ∴ (A + B)'s 1 day's work $latex = \frac{1}{20} + \frac{1}{30} = \frac{3+2}{60} = \frac{1}{12}&s=1$ So, the work will be completed in 12 days if they work together. Hence option [B] is correct answer.

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