If you spend 8,000 yuan on a CCB credit card and apply for 3 installments of repayment, the interest calculation method is as follows:

1. First, when applying for 3 installments of repayment, the repayment amount for each installment is 8,000 yuan/3 issues = 2,666.67 yuan.

2. Secondly, the interest calculation method of CCB credit card is daily interest, and the specific interest rate is determined according to the user's personal credit situation. Generally, for customers with good credit, the interest rate will float at a certain percentage above the base interest rate.

3. Assuming that the customer's credit is good and the CCB credit card base interest rate is 6 per year, the daily interest calculation formula is: repayment amount per period * (interest rate / 365 days) * 30 days.

4. Therefore, the interest per period is calculated as: 2666.67 yuan * (6/365) * 30 = 49.18 yuan.

5. Summary: Based on the above calculation, if the customer applies for 3 installments of repayment, and the repayment amount of each installment is 2666.67 yuan, then the interest for each installment is 49.18 yuan.

Extended information:

The interest calculation is based on the daily balance. If the consumption is completed, the interest on the first day will be generated and accumulated until the final repayment date. Therefore, if you choose to repay in installments, since interest will accrue every day, the total interest will be more than if you repay the loan in full at once.

The above is the interest calculation and explanation based on the situation of applying for three installments for a CCB credit card consumption of 8,000 yuan.