Correct Answer - Option 1 : 36 days

**Given: **

Danish and Dolly can complete the work = 20 days

Danish is 25% more efficient than Dolly.

**Calculation:**

Danish ∶ Dolly

Efficiency 125 ∶ 100

5 ∶ 4

Time 4 ∶ 5

Work completed in days = 20

⇒ Units work done in day = 4+5 =9 units

⇒ Total work done in 20 days = 20 × 9 = 180 units

⇒ Time taken by Danish = 180/5 = 36 days

∴ Danish will complete this task alone for 36 days.

The correct option is 1 i.e. 36 days.