Correct Answer - Option 2 : 18

**Given **

Aman can do work = 30 days

**Formula Used **

Work = time × efficiency

**Calculation**

Let the efficiency of Aman, Parul and Charu be A, P and C respectively

⇒ A : P = 2 : 1

⇒ P : C = 3 : 1

⇒ A : P : C = 6 : 3 : 1

⇒ So, total work = 6x × 30 = 180x

⇒ Now, calculate number of days to complete the work when they work all together

⇒ Total efficiency = 10x

⇒ No. of days = total work/ total efficiency

⇒ 180x/10x = 18 days

**∴ 18 days is required to complete the work when they work all together.**