Add and subtract fractions with the denominator, the denominator remains the same, and only the numerator is added and subtracted. As a result of calculation, we can divide an approximate quotation into the simplest scores. For addition and subtraction of fractions with different denominators, divide the fractions first, and then add and subtract the fractions with the same denominator.

Calculation method of fractional addition and subtraction with integers: Integer and true fraction are added and directly written as fractions. Integer and false fraction are added, and the false fraction is written as a fraction or integer first, and then added. Subtract an integer from a true fraction, write the integer as a false fraction with the same denominator as the fraction, and then subtract.

Note: General fractions generally seek the least common multiple of denominator. Scores with scores cannot be false scores.

When adding, if the items in the formula can be grouped properly, the calculation process will be greatly simplified. When two numbers are added, if their total is exactly ten, one hundred, one thousand, ten thousand ... then calculate first.

For example,1+9 =10,3+7 =10,2+8 =10,4+6 =10,5+5 =10. Another example: 2 1+79= 100, 44+56= 100, or 55+45= 100. In the above formula, 1 is called the "complement" of 9; 79 is called the "complement" of 2 1, and 44 is also called the "complement" of 56, which means that two numbers are "complements" of each other.

In a formula with only addition and subtraction operations, if there is a "+"sign in front of the brackets, the operation symbols in the brackets will remain unchanged whether the brackets are removed or added; If there is a "-"sign in front of the bracket, whether the bracket is deleted or added, the operation symbol in the bracket will change, and "+"will change to "-"and "-"will change to "+".

Learning addition and subtraction is the foundation. The so-called foundation includes two aspects, one is to lay a good foundation for improving speed, and the other is to lay a good foundation for learning multiplication and division. If the foundation of addition and subtraction is not well laid, the speed will not increase. Without the basis of addition and subtraction, multiplication and division can't learn well.

Because of the flexibility of addition and subtraction, we need to learn the skills and methods of addition and subtraction flexibly according to the characteristics of the topic, which can not only simplify the operation process and reduce the amount of calculation, but also improve the operation speed, shorten the calculation time and get twice the result with half the effort.