Fixed investment is the abbreviation of fixed-term investment fund, which refers to investing a fixed amount (such as 500 yuan) in a designated open-end fund at a fixed time (such as the 8th of each month), similar to the bank's deposit and withdrawal method. People usually refer to funds mainly as securities investment funds.

Complete calculation formula of the fund's fixed investment income:

m=a( 1+x)[- 1+( 1+x)^n]/x；

M: expected income;

A: the amount of fixed investment in each period;

X: rate of return;

N: fixed investment period (n power in the formula).

Pay attention to the matching of A, X and N, and calculate the monthly fixed investment amount, monthly yield and fixed investment month. If it is one year, it will be counted after reunification.

Suppose 300 yuan invests 3600 yuan every month, with an annual income of 15%, and invests for 35 years.

3600 (1+15%) [-1+(1+15%) 35]/15% = 3648044 yuan.

From the perspective of investment, the return on investment calculated by compound interest is quite amazing. Many people know the formula of compound interest: the sum of principal and interest = principal ×( 1+ interest rate) periods. As for the concept of compound interest, it is the easiest to understand if it is explained by what is generally called "rolling interest". That is, add the interest or profit earned with money to the principal and continue to earn remuneration.

So if you invest with compound interest, the final return is the result of multiplying the yield per period by the principal. The more periods (that is, the earlier they start), the greater the profit.