How to check addition and subtraction, and how to check addition and subtraction

The four operations are usually checked by the inverse of the equation.

Addition is checked by subtraction, and subtraction is checked by addition.

For example. Addition formula: a+b=c, can be checked with c-a=b or c-b=a;

Subtraction: a-b=c, can be checked with c+b=a.

Addition can be checked by subtraction, and subtraction can be checked by subtraction and addition.

You can turn the two numbers upside down and add them together to see if the result is the same as the original result, the same is true, and the different is wrong.

There are 5 ways to check addition and subtraction:1. Addition is checked by subtraction, such as 17+8=25, and 25-8=17.

2. The addition is checked by multiplication, such as 15+15+15=45, and the calculation is 15x3=45.

3. Subtraction is checked by addition, for example, 87-19=68, 68+19=87.

4. Subtraction is calculated with a mixture of addition and subtraction, such as 54-18=36, and 36+20-2=56-2=54

5. Addition and subtraction are used for mixed calculation, such as 79+89=168, and 168-90+1=78+1=79.

There are two different methods for checking addition and subtraction.

The calculation method of addition: one is to exchange the position of the addition and calculate it again; One is and subtract one addition to equal the other.

The calculation method of subtraction: one is that the difference plus or minus is equal to the subtracted number; One is that the difference between the subtraction is equal to the subtraction.

The first subtraction check: In the subtraction check, we can check by subtracting the difference from the subtracted number.

The second subtraction check: In the subtraction operation, we can also use the difference plus or minus for the check.

The first method of addition check: In addition, we can use the position of two additions to be reversed.

The second addition method: In addition, we can also use and subtract one of the additions to check the spring line.

Detailed analysis: Addition formula, which can be checked by subtraction. The equation in the figure below is used as an example, and the advanced annihilation is calculated vertically.

Addition is checked by subtraction, using and subtracting one addition from its Sen key to see if it is equal to another addition.

Subtraction is checked with addition, and the vertical type is written first.

The difference is added to the subtraction to see if it is equal to the subtracted number.

To sum up, it is the addition with the subtraction check, and the subtraction with the addition check. Developing a good habit of checking calculations is more conducive to the correctness of calculations.

Pay more attention to oral arithmetic practice, not only to improve the accuracy, but also to speed up the speed of oral arithmetic. In the usual calculation, pay attention to the calculation, which can increase the accuracy of the problem.

It is shown below. 1.The calculation method of the plus transport imitation method: one is to exchange the position of the number of late and quiet closures, and calculate it again; One is and subtract one addition to equal the other.

2.The calculation method of subtraction: one is that the addition and subtraction of differential code cracking is equal to the subtracted number; One is that the difference between the subtraction is equal to the subtraction.

3.Subtraction is a mixture of addition and subtraction, for example, 54-18=36, 36+20-2=56-2=54

Hope, thank you.