1. **Problem Statement:** Calculate the simple interest earned on a principal amount over a certain period at a given rate. 2. **Formula:** Simple Interest (SI) is calculated using the formula: $$SI = \frac{P \times R \times T}{100}$$ where $P$ is the principal amount, $R$ is the annual interest rate (in %), and $T$ is the time in years. 3. **Explanation:** Simple interest is the interest calculated only on the original principal, not on accumulated interest. 4. **Example:** Suppose you invest $P=1000$, at an interest rate $R=5\%$ per year, for $T=3$ years. 5. **Calculation:** $$SI = \frac{1000 \times 5 \times 3}{100} = \frac{15000}{100} = 150$$ 6. **Interpretation:** The interest earned after 3 years is 150. 7. **Total Amount:** The total amount $A$ after $T$ years is: $$A = P + SI = 1000 + 150 = 1150$$ This means you will have 1150 after 3 years including the interest.