Different countries have different price levels and common currencies, so the monetary relationship between the two countries cannot be 1 to 1, that is, it is impossible to change 1 USD into 1 RMB. In fact, money is also a commodity. Things are rare, and the less, the more valuable. But you can't pay too little, otherwise it will lead to deflation, so the price of apples in RMB will be different.

The exchange rate exists to balance the two. One is to reflect the real price that a country is willing to pay for another commodity; Second, we must ensure that domestic enterprises can make money, thus promoting the development of the domestic economy. As far as the former is concerned, for example, the RMB is 4: 1 to the US dollar, which means that China people would rather pay four times the tuition than go to the United States for education, while Americans are only willing to pay a 3/4 price discount for goods from China. So this is the real demand. Although the United States has a great demand for China's commodities, which makes China's overall foreign exchange reserves of US dollars large, every commodity is a bargain. As far as the latter is concerned, for example, Japan is pursuing the demand of foreign goods, signing the Plaza Agreement, and the appreciation of the yen has made domestic enterprises unable to make money, resulting in losses for almost 30 years.