If you deposit 800 yuan in the bank, the interest tax will be 20%. After one year, you will get 814.4 yuan of principal and after tax interest. What's the annual interest rate of fixed deposit for one year?
After tax interest = principal × interest rate × term × (1-tax rate)
Annual interest rate = (sum of principal and interest - Principal) × principal / term / (1-tax rate)
Annual interest rate = (814.4-800) × 800 / 1 / (1-20%) = 0.0225 = 2.25%
The annual interest rate of time deposit is 2.25%