Good friends1919,2828, hand in hand, 3737 is really close, and 4646 will go together. Make a pair of hands in half. One plus nine, ten tadpoles, two plus eight, ten old ducks, three plus seven, ten old hens, four plus six, ten golden monkeys, five plus five, and ten big tigers.

Basic concepts of addition and subtraction;

Addition is a mathematical operation that describes the sum of two or more quantities. The basic properties of addition are interchangeability and combination, that is, a+b=b+a and (a+b)+c=a+(b+c). The symbol of addition is "+",which means that two or more numbers are added. For example, 2+3=5, which means that 2 and 3 add up to get 5.

Subtraction is a mathematical operation that describes the difference between two quantities. The basic properties of subtraction are anti-commutativity and associative law, that is, a-b=-(b-a) and (a-b)-c=a-(b+c). The sign of subtraction is "-",which means subtracting another number from one number. For example, 5-3=2, which means that 5 MINUS 3 gets 2.

Application of addition and subtraction;

Addition and subtraction are widely used in mathematics, such as algebra, geometry, trigonometric functions and so on. In algebra, addition and subtraction can be used to describe the relationship and change between variables; In geometry, addition and subtraction can be used to calculate the area, perimeter and so on of a figure. In trigonometric function, addition and subtraction can be used to describe the relationship and change between angle and length.

Addition and subtraction can also be used to solve various practical problems, such as shopping, calculation time, calculation speed and so on. Addition and subtraction is one of the basic operations in mathematics and plays a very important role in mathematics.

Although addition and subtraction are one of the most basic mathematical operations, there are mathematical concepts and ways of thinking behind them. By learning and mastering the calculation rules and application of addition and subtraction, we can better understand and master mathematical knowledge and cultivate mathematical thinking ability and problem-solving ability.