when the fund is bought at different times, it is calculated based on the net value of the fund on different working days. After the purchase, an average purchase cost can be known. When it is redeemed, the fund company naturally calculates the average cost and the net value of the redeemed fund. When the investor redeems 5% of the principal, it will get 5% of the total income at the same time.

1. Fund refers to a certain amount of funds set up for a certain purpose in a broad sense. It mainly includes trust and investment funds, provident funds, insurance funds, retirement funds and funds of various foundations.

2. According to different standards, securities investment funds can be divided into different types:

(1) According to whether fund units can be increased or redeemed, they can be divided into open-end funds and closed-end funds. Open-end funds are not traded on the market (it depends on the situation), and the fund size is not fixed through subscription and redemption by banks, brokers and fund companies; Closed-end funds have a fixed duration, generally listed and traded in securities exchanges, and investors buy and sell fund units through the secondary market.

(2) According to different organizational forms, it can be divided into corporate funds and contractual funds. Funds are established by issuing fund shares to establish investment fund companies, which are usually called corporate funds; Fund managers, fund custodians and investors are established through fund contracts, which are usually called contractual funds. China's securities investment funds are all contractual funds.

(3) According to the difference of investment risks and returns, it can be divided into growth funds, income funds and balanced funds.

(4) According to different investment objects, it can be divided into stock funds, bond funds, money market funds, futures funds, etc.

3, closed-end funds, because closed-end funds are traded in the stock exchange by bidding, the transaction price is affected by the relationship between market supply and demand and does not necessarily reflect the net asset value of the fund, that is, the transaction price of closed-end funds has a premium or discount phenomenon relative to its net asset value. The practice of foreign closed-end funds shows that the transaction price often has the price fluctuation law of premium first and then discount. Judging from the operation of closed-end funds in China, no matter how the fundamental situation changes, the transaction price trend of closed-end funds in China has never been separated from the price fluctuation law of premium first and then discount.