Conclusion: If you have a loan or deposit with a principal of 100,000 yuan and an annual interest rate of 8%, or 0.8%, then the calculation of interest for one year is very simple. According to the interest calculation formula, interest is equal to the principal multiplied by the annual interest rate. Specific to this example, it is 100,000 yuan multiplied by 0.8%, which is equal to 800 yuan. This calculation is based on the multiplication of percentages. Whether it is an integer or a decimal, it can be performed according to the multiplication rules: starting from the ones digit, multiplying digits one by one, and the decimal part is determined according to the number of digits after the decimal point. Therefore, your annual interest income will be 800 yuan. For more complex calculations, such as those involving compound interest or the deduction of interest taxes, more detailed formulas may need to be used, but the basic annual interest calculation is the result.