A can complete a piece of work in 18 days, and B can do it in 27 days.
If they work together, how many days will they take to complete the work?

Correct option is A

Given
Time taken by A = 18 days
Time taken by B = 27 days

Formula Used
If A can do a work in x days and B can do it in y days, together they can complete it in  $$\frac{x \times y}{x + y} \ days.$$​​

Solution
Using the direct formula for combined work:
Time taken together = $$\frac{18 \times 27}{18 + 27}$$​

Time taken together =  $$\frac{486}{45}$$​​
Time taken together = 10.8 days

Final Answer
So the correct answer is (a)