The next four operations for the fourth grade 2 What are the four operations for the fourth grade

The fourth refers to the calculation rules of addition, subtraction, multiplication, and division.

In mathematics, when the first-level operation (addition and subtraction) and the second-level operation (multiplication and division) appear in a formula at the same time, their order of operation is first multiplication and division, then addition and subtraction, if there are parentheses, first count the parentheses in the brackets and then count the parentheses, the same level of operation order is from left to right, such operations are called four operations.

The rule of four operations:

1. Calculation rules for addition and subtraction of integers:

1) To align the same digits, add or subtract the numbers on the same counting unit;

2) Whoever reaches the age of ten will advance to the previous one.

2. Calculation rules of decimal addition and subtraction:

1) Calculate the addition and subtraction of decimals, first align the decimal points of each number (that is, align the numbers on the same digit), 2) then calculate according to the rules of addition and subtraction of integer numbers, and finally align the decimal point on the horizontal line in the obtained number.

There is a 0 at the end of the decimal part of the number, and the 0 should be removed in general. ）

3. Calculation rules for addition and subtraction of fractions:

1) When the denominator is the same, only the numerator is added and subtracted, and the denominator remains unchanged;

2) When the denominator is not the same, it is necessary to divide the fraction with the same denominator first, and then add and subtract.

4. Integer multiplication rule:

1) From the right, multiply the first factor by the number on each of the second factor, and the end of the number will be aligned with which digit of the second factor is the same as which digit of the second factor;

2) Then add up the numbers that you have multiplied several times.

Multiply with 0 at the end of an integer: you can first multiply the numbers before 0, and then see how many zeros there are at the end of each factor, and add a few zeros to the end of the multiplied number. ）

5. Decimal multiplication rule:

1) Calculate the product according to the rule of integer multiplication;

2) If you look at how many decimal places there are in the factor, count the number from the right side of the number, and point to the decimal point.

3) There is 0 at the end of the decimal part of the number, and the 0 should be removed in general.

6. The law of fraction multiplication: multiply the numerator of each fraction as the numerator, and multiply the denominator of each fraction as the denominator, (that is, multiply the reciprocal of the fraction), and then reduce the fraction.

7. The division rule of integers.

1) Start from the quotient of the dividend, first see how many digits there are in the divisor, and then use the divisor to try to divide the first few digits of the dividend, if it is smaller than the divisor, try to divide by one more digit;

2) Divide to the digit of the dividend, write the quotient on that digit;

3) The remaining number after each division must be smaller than the divisor.

8. The divisor is the decimal division rule of an integer:

1) Remove according to the law of integer division, and the decimal point of the quotient should be aligned with the decimal point of the dividend;

2) If there is still a remainder at the end of the dividend, add zero after the remainder and continue dividing.

9. The divisor is the decimal division rule for decimals:

1) First look at how many decimal places there are in the divisor, move the decimal point of the dividend to the right by a few places, and make up with zero if the number is not enough;

2) Then divide by decimal division where the divisor is an integer.

10. The division rule of fractions:

1) Multiply the numerator of the dividend by the denominator of the divisor as the numerator;

2) Multiply the denominator of the dividend by the numerator of the divisor as the denominator. Share.

What are you going to ask, questions?

Addition, subtraction, multiplication, and division are collectively referred to as the Four Operations.

1. The calculation method of the four operations:

1) In equations without parentheses, if there is only addition and subtraction or only multiplication and division, the limbs should be calculated in order from left to right.

2) In the equation without parentheses, there are multiplication, division, addition and subtraction, and multiplication and division must be calculated first, and then addition and subtraction.

3) The formula has parentheses, and the inside of the brackets should be counted first, and then the outside of the brackets; The equations in parentheses are calculated in the same order as above.

2. About the operation of "0":

1) "0" cannot be used as a divisor; The letter indicates: A 0 error.

2) Add 0 to a number to get the original number; The word hail mother means: a+0=a.

3) Subtract 0 from a number to get the original number; The letters indicate: a-0=a.

4) The subtracted number is equal to the subtracted number, and the difference is 0; The letters indicate: a-a=0.

5) Multiply a number by 0 to get 0; The letter indicates: a 0 = 0.

6) 0 divided by any number other than 0, and 0; The letter indicates: 0 a(a≠0)=0.

Considerations for 4th Grade Math:

1. Don't do difficult questions.

Fourth-grade children are highly motivated to learn, and difficult questions often discourage them. Therefore, you can follow the teacher's progress step by step, and the problems beyond the existing difficulty will naturally be contacted in the future study, step by step, and it is also a planned deployment for your own learning.

In addition, in the fourth grade of primary mathematics, the beginning of the exposure to abstract knowledge has been strengthened, but too abstract or too technical requirements can also be omitted. At the same time, this is also a requirement to do one step at a time, learn steadily, and don't practice running or even jumping if you don't learn to walk, which is often counterproductive.

2. Integrate the content of the textbook.

It is necessary to master the things in the mathematics textbook thoroughly, and this criterion is: to make all the exercises involved in the textbook without difficulty.

Specifically, actively cooperate with the teacher's teaching on the topic; Do not pile up problems, and if there are problems, they must be solved in time; The homework must be completed according to the quality and quantity, and strive to achieve "today's work is completed today".

Multiplication first, subtraction later. 988-468=520。

Merge similar terms (38-28) x 26 = 520

125－25×6 （135＋75）÷（14×5） 120－60÷5×5

I've been playing for a long time, I don't know if it will help you? Please choose me. Please give me extra points.

Will be cold and crying, wet people, think about him, I, think about me, think about me, the family is so regular, ktvkkkkkk, oh, woo, stop.

1. 620 trees were watered in the third and fourth grades of a primary school, and 40 trees were watered every day for 8 days in the third grade; The rest is watered by the fourth grade, and it will be watered in 5 days, how many trees are watered per day on average?

2 3 looms weave 336 meters in 4 hours, according to this calculation, how many meters does 1 loom weave in 8 hours?

3 A and B are 560 kilometers apart, and one car travels 48 kilometers per hour from A to B, and the other car travels 32 kilometers per hour from B to A.

4 A section of the road was originally planned to be repaired in 20 days The actual daily repair was 45 meters more than the original plan, and the task was completed 5 days ahead of schedule How many meters of road was originally planned to be repaired per day?

A section of the road was originally planned to be repaired in 20 days, but it was actually repaired 45 meters more than the original plan every day, and the task was completed 5 days ahead of schedule How many meters of road was originally planned to be repaired per day?

Knowledge point 1:

1. Same-level operations (only including addition and subtraction, or only multiplication and division), calculated from left to right.

2. In the same operation, there are both addition and subtraction, as well as multiplication and division, and multiplication and division must be calculated first, and then addition and subtraction.

3. In mixed operations with parentheses, the inside of the brackets is counted first, and then the outside of the brackets is counted.

4. When solving practical problems, we must consider the application of parentheses.

5. Calculations related to 0 (add 0 to a number to get this number, subtract 0 from a number to get this number, multiply a number by 0 to get 0, 0 cannot be used as a divisor.)

Knowledge point 2: the law of operation and simple operation.

1. Additive associative law: a+b+c=a+(b+c).

Commutative law of addition: a+b=b+a

2. Multiplicative commutative law: a b = b c

Multiplicative associativity: a b c = a (b c).

Multiplicative distributive property: (a+b) c=a c+b c

The inverse of the multiplicative distributive property: a c+b c=(a+b) c