Correct Answer - Option 2 : 48 years

**Given: **

Amount = 4 times of principal

Rate of interest = \(6\frac{1}{4}%\)% p.a.

**Formula Used:**

Simple interest = Amount - Principal

Simple interest = Principal × Time × Rate of interest/100

**Calculation:**

Let assume the principal be x

Amount = 4x

Simple interest = Amount - Principal

⇒ Simple interest = 4x - x = 3x

Simple interest = Principal × Time × Rate of interest/100

⇒ 3x = x × Time × (25/4)/100

∴ Time = 48 years

The correct option is 2 i.e. 48 years