Correct Answer - Option 2 : 105/13 days

**Given:**

A is 30% more efficient than B.

C is 20% more efficient than B.

**Concept used:**

Total Work = Efficiency × Time

**Calculation:**

Let the efficiency of B be 100.

Efficiency ratio,

A ∶ B = 130 ∶ 100 ---(1)

B ∶ C = 100 ∶ 120 ---(2)

From equation (1) and (2), we get

A ∶ B ∶ C = 130 ∶ 100 ∶ 120

A ∶ B ∶ C = 13 ∶ 10 ∶ 12

Total Work = Efficiency × Time

Total Work = (13 + 10 + 12) × 5 = 35 × 5 = 175

Time_{A} = [3/4^{th} of the total work]/Efficiency of A

Time_{A} = {(3/5) × 175}/13

Time_{A} = 105/13 day

**∴ 'A' alone complete 3/5**^{th} of the total work in 105/13 days.