Ravi can complete a task in 6 days and Mohan can complete the same task in 9 days. In how many days can Ravi and Mohan together complete the same task?

Let the total work be W

Number of days required for Ravi to complete the task = 6 days

$$\Rightarrow$$  Work done by Ravi in 1 day = $$\frac{W}{6}$$

Number of days required for Mohan to complete the task = 9 days

$$\Rightarrow$$  Work done by Mohan in 1 day = $$\frac{W}{9}$$

Work done by Ravi and Mohan together in 1 day = $$\frac{W}{6}+\frac{W}{9}$$ = $$\frac{15W}{54}$$ = $$\frac{5W}{18}$$

$$\therefore\ $$Number of days required for Ravi and Mohan together to complete the task = $$\frac{\text{Total work}}{\text{work done in 1 day}}$$ = $$\frac{W}{\frac{5W}{18}}$$ = $$\frac{18}{5}$$

= $$3 \frac{3}{5}$$ days

Hence, the correct answer is Option A