A and B can do a piece of work in 30 days. B is 2 times efficient than A. Find the number of days taken by  A and B individually to do the same piece of work.

Correct option is A

Given:
A and B together can complete the work in 30 days. B is 2 times efficient than A. We need to find the number of days taken by A and B individually to complete the work.
Solution:
Let the efficiency of A be x, so the efficiency of B will be 2x, as B is 2 times efficient than A.
Together, A and B complete the work in 30 days, so their combined efficiency is $$\frac1{30}$$​ work per day.
Thus,

​$$x + 2x = \frac{1}{30}$$ ​
3x = $$\frac1{30}$$ 

x= $$\frac1{90}$$​​

The number of days taken by A to complete the work is $$\frac1x = 90 \text{days}.$$​​
The number of days taken by B to complete the work is $$\frac1{2x} = 45 \text{days}.$$​
Thus, A takes 90 days and B takes 45 days to complete the work individually.