1, addition and subtraction is one of the earliest mathematical operations, which can be traced back to ancient civilizations such as Egypt and Babylon. In history, addition and subtraction were originally invented to solve problems in daily life. For example, in business transactions, addition and subtraction are used to calculate the quantity and price of goods. With the development of mathematics, addition and subtraction has gradually become a basic concept in mathematics and has been widely used in various fields.
2. Addition is the operation of combining two or more arrays into a sum. Expressed by mathematical symbols: a+b=c, where A and B are two addends and C is their sum.
3. Subtraction is the operation of subtracting one number from another. Expressed by mathematical symbols: a-b=c, where A is the minuend, B is the minuend, and C is their difference.
4. In addition and subtraction, the same numbers should be aligned first. This can help us find the position of each number more quickly, thus reducing the calculation error.
5. Calculate from low to high. When adding and subtracting, it is calculated from low to high. This can ensure that each number is processed correctly and avoid mistakes.
6. When performing subtraction by borrowing carry, if the minuend is less than the minuend, you need to borrow from the high position; If the minuend is greater than the minuend, it needs to be rounded up to a low level. Borrowing and carrying are important skills in addition and subtraction, which need to be handled carefully.
7. Group calculation When adding and subtracting large numbers, you can calculate numbers in groups. For example, you can divide each number into tens, hundreds, thousands, etc. , and then add and subtract respectively. In this way, results can be obtained faster and errors can be reduced.
8. Oral arithmetic and mental arithmetic are commonly used skills in addition and subtraction. By mastering some common number combinations and calculation rules, you can quickly calculate the results orally or mentally. For example, 20+30 = 50,99+1=100 and so on.