Question

A sum becomes double in 8 years at simple interest. What is the rate percent per annum?

• A. 12%
• B. 8%
• C. 1(2)5%
• D. 7.5%

Hint:

To find the rate of interest in simple interest problems, use the formula \( A = P + \frac{P \times R \times T}{100} \), and substitute the given values.

Answer 1

The Correct Option is C

Let the principal be \( P \). After 8 years, the sum becomes double, so the amount is \( 2P \). The formula for simple interest is: \[ A = P + \frac{P \times R \times T}{100}, \] where \( A \) is the amount, \( P \) is the principal, \( R \) is the rate of interest, and \( T \) is the time period. Since \( A = 2P \) and \( T = 8 \), we substitute into the formula: \[ 2P = P + \frac{P \times R \times 8}{100}. \] Simplifying: \[ 2P - P = \frac{P \times R \times 8}{100} \quad \Rightarrow \quad P = \frac{P \times R \times 8}{100} \quad \Rightarrow \quad R = 12.5. \]