Correct Answer - Option 4 : 4%

Given:

The Sum of money doubles itself in 25 years.

Concept:

Simple interest is the interest calculated on the principal portion of the loan or the original contribution to the saving account.

Formula Used:

Simple Interest = (P × R × T)/100

S.I = Amount - Sum

Calculation:

Let the sum be 'P' then Amount after 25 years = 2P

S.I = 2P - P = P

P = (P × R × 25)/100

⇒ R = 100/25 = 4%

∴ The rate of interest per annum is 4%.