Q. A can do a work in 6 days and B in 9 days. How many days will both take together to complete the work?
Answer: 3.6 days
Notes: According to question. A can finish the whole work in 6 days. ∴ A's one day's work =$latex \frac{1}{6}&s=1$ Similiarly, B's one day's work =$latex \frac{1}{9}&s=1$ (A+B)'s one day's work = $latex \left ( \frac{1}{6}+\frac{1}{9} \right )=\left ( \frac{3+2}{18} \right )=\frac{5}{18}&s=1$ Therefore, (A+B) can finish the whole work in $latex \frac{18}{5}&s=1$ days i.e. 3.6 days. Hence option [C] is the right answer.

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