update: README.md to improve description and add formula for simple interest calculation

Author: dicky2ux

README.md

@@ -2,15 +2,28 @@
 
 ## Simple Interest Calculator
 
-A calculator that calculates simple interest given principal, annual rate of interest and time period in years.
-
-```
-Input:
-   p, principal amount
-   t, time period in years
-   r, annual rate of interest
-Output
-   simple interest = p*t*r
-```
-
-_© 2022 XYZ, Inc._
+A calculator that computes **simple interest** given the principal amount, annual rate of interest, and time period in years.
+
+### Formula
+\[
+\text{Simple Interest} = \frac{P \times R \times T}{100}
+\]
+
+Where:  
+- **P** = Principal amount  
+- **R** = Annual rate of interest (in %)  
+- **T** = Time period (in years)  
+
+### Example
+
+**Input:**
+- Principal (P) = 1000  
+- Rate (R) = 5%  
+- Time (T) = 2 years  
+
+**Output:**
+- Simple Interest = (1000 × 5 × 2) / 100 = **100**
+
+---
+
+© 2022 XYZ, Inc.