How to calculate interest rate

 To calculate interest rate, you need the following information:

1. Principal amount (the initial amount of money)
2. Final amount (the amount after interest)
3. Time period (the duration for which the interest is calculated)

You can use the following formula to calculate the interest rate:

$\text{Interest Rate}=\left(\frac{\text{Final Amount}-\text{Principal Amount}}{\text{Principal Amount}}\right)\times \left(\frac{1}{\text{Time Period}}\right)\times 100$

Here's how you can calculate it step by step:

1. Subtract the Principal Amount from the Final Amount.
2. Divide the result by the Principal Amount.
3. Divide the above result by the Time Period.
4. Multiply the final result by 100 to express it as a percentage.

This will give you the interest rate as a percentage.