Keerthi and Malathi together can complete a task in 12 days, while Malathi can finish it in 30 days. In how many days can Keerthi alone complete the task?

Correct option is B

Given:

- Keerthi and Malathi together complete the task in 12 days
- Malathi alone completes the task in 30 days
Concept Used:

- Work done = Rate × Time
- Work rate of two people working together = Sum of individual work rates
- Individual work rate = $$\frac{1 }{Time \ taken}$$​​
Solution:

Let the total work be 1 unit.
Combined work rate of Keerthi and Malathi:
​$$\frac{1}{12} work/day$$​​
Work rate of Malathi alone:
$$\frac{1}{30}$$​ work/day
Work rate of Keerthi alone:
​$$\frac{1}{12} - \frac{1}{30} = \frac{5 - 2}{60} = \frac{3}{60} = \frac{1}{20}$$​​

Therefore, Keerthi alone can complete the task in 20 days.

Keerthi can complete the task in 20 days.