3rd grade math fast oral arithmetic methods, 3rd grade clever arithmetic quick arithmetic methods

As long as you are proficient in the calculation rules and operation sequence, according to the characteristics of the problem itself, use reasonable and flexible calculation methods, simplify the complex, and make the difficult easy, you can calculate quickly and accurately. First of all, I will introduce you to 5 quick calculation skills:

1.Method 1: Symbolic moving.

When a calculation problem has only the same level of operations (only multiplication and division or only addition and subtraction) and no parentheses, we can "move with signs". For example:

2.Method 2: Combine the Law.

Bracketed method. 1) When adding parentheses in addition and subtraction operations, the parentheses are preceded by a plus sign, the parentheses are unchanged, the parentheses are preceded by a minus sign, and the parentheses should be changed. For example:

2) When adding parentheses to the multiplication and division operation, the parentheses are preceded by the multiplication sign, the parentheses are unchanged, and the parentheses are preceded by the division sign.

Change the sign in parentheses. For example:

De-bracket method. 1) When removing parentheses in addition and subtraction operations, the parentheses are preceded by the plus sign, the parentheses are removed and the parentheses are unchanged, and the parentheses are preceded by the minus sign, and the parentheses are removed to change the sign (the addition in the original parentheses is now to be subtracted; It used to be minus, but now it is going to be added). For example:

2) When removing parentheses in the multiplication and division operation, the parentheses are preceded by the multiplication sign, the parentheses are removed and the invariant sign is removed, and the division sign is preceded by the parentheses. It used to be dividing, but now it is going to be multiplied. For example:

3.Method 3: Multiplication of the law of distribution.

Distributive method. In parentheses is an addition or subtraction operation, multiplying with another number, pay attention to the distribution. For example:

Extracting the common factor method.

Note the extraction of the same factor. For example:

4.Method 4: Rounding method.

When you see the name, you know what this method means. When using this method, you need to pay attention to observation and find patterns. Also pay attention to repaying, there is borrowing and repaying, it is not difficult to borrow again. For example:

5.Method 5: Splitting method.

The splitting method is to split a number into several numbers for the convenience of calculation. This requires mastering some "good friends" such as: 2 and 5, 4 and 5, 4 and 25, 8 and 125, etc. Be careful not to change the size of the number in the split. For example:

In order for children to become proficient in using quick arithmetic methods, they need to improve their numeracy skills through consistent practice, so that they can be comfortable with both homework and exams.

It is recommended that parents set aside 5 minutes a day to help their children practice oral arithmetic and cultivate their children's ability to do oral arithmetic quickly and accurately. In the process of practice, it is also necessary to record the time when it is easy to use, check the correctness and error immediately after doing it, and analyze the reasons for the error.

1.Method 1Carry addition of two digits plus two digits.

Formula: Add 9 to subtract 1, add 8 to subtract 2, add 7 to subtract 3, add 6 to subtract 4, add 5 to subtract 5, add 4 to subtract 6, add 3 to subtract 7, add 2 to subtract 8, add 1 to subtract 9. (Note:.)

The number of additions in the oral duel is to say the number in the single digit). 2.Method 2

Abdication subtraction of two digits minus two digits. Verbal decision: minus 9 to add 1, minus 8 to add 2, minus 7 to add 3, minus 6 to add 4, minus 5 to add 5, minus 4 to add 6, minus 3 to add 7, minus 2 to add 8, minus 1 to add 9.

Some of the more conventional methods in the third-grade quick arithmetic methods are multiplication, commutative law, and so onThe associative law of multiplicationand some other related quick calculation methods, which are the most conventional calculations, and there are some methods with tricks.

Then there are some relatively novel methods, which can be to understand a method like the grouping method, which is to divide some numbers of the same class into a group, and then you can perform relative operations, and then in the grouping method, in order to simply group, the grouping has a surplus, complex grouping and some other types.

In addition to this kind of relatively novel grouping method, there is also a way to sum the pyramid number series, such as Shi Mengguo, it may be more difficult to accept, because you need to draw the reputation to talk about the relevant figures, to be able to understand how this calculation method is implemented. So the above are some of the methods of clever and quick calculation in the third grade.

1. "Rounding" is calculated first.

1.Calculation: (1) 24 + 44 + 56 (2) 53 + 36 + 47. Clever stopping.

Solution: (1) 24 + 44 + 56 = 24 + (44 + 56) = 24 + 100 = 124.

Since 44+56=100 is a whole hundred, let's calculate the sum of them first.

Since 53+47=100 is a whole hundred, move +47 with the symbol first, and move it before +36; Then calculate the sum of 53+47.

2.Calculation: (1) 96 + 15 (2) 52 + 69.

Solution: (1) 96 + 15 = 96 + (4 + 11).

Split 15 into 15 = 4 + 11, this is because 96 + 4 = 100, which can be rounded up first.

Because 69 + 31 = 100, so split 52 into the sum of 21 and 31, and then round up and Hu 31 + 69 = 100 to calculate first.

2. Change the order of operations.

In mixed equations with only the "+" sign, the order of operations can be changed.

Calculation: (1) 45-18+19 (2) 45+18-19.

Solution: (1) 45-18 + 19 = 45 + 19-18 = 45 + (19-18) = 45 + 1 = 46.

Move +19 with the symbol, in front of -18. Then count 19-18=1 first.

The result of adding 18 minus 19 is equal to subtracting 1.

3. Calculate the sum of the continuum of the continuum of differences.

A string of numbers where the difference between two adjacent numbers is equal is called an equal difference continuous number, also called an equal difference series, such as:

4, 8, 12, 16, 20, and so on are all contiguous continuums.

When the number of contiguous consecutive numbers is odd, their sum is equal to the middle number multiplied by the number, which is simply denoted as:

1) Calculation: 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 = 5 (the middle number is 5) 9 (9 numbers in total) = 45.

2) Calculation: 1 + 3 + 5 + 7 + 9 = 5 (the middle number is 5) 5 (5 numbers in total) = 25.

3) Calculation: 2 + 4 + 6 + 8 + 10 = 6 (the middle number is 6) 5 (5 numbers in total) = 30.

4) Calculation: 3 + 6 + 9 + 12 + 15 = 9 (the middle number is 9) 5 (there are 5 numbers in total) = 45.

5) Calculation: 4 + 8 + 12 + 16 + 20 = 12 (the middle number is 12) 5 (5 numbers in total) = 60.

4. Benchmark number method.

1) Calculation: 23 + 20 + 19 + 22 + 18 + 21.

Solution: If you look closely, the size of each addition is close to 20, so you can add each addition by 20 first, and then add the less and subtract the overcount.

The 6 additions are added according to 20, and the sum = 20 6 = calculated by 20 is less "3", so "3" is added; 19 adds "1" according to 20, so subtract "1" and so on.

The third-grade method of quick arithmetic is the commutative law of additionAssociative LawMake the calculations.

Formula. Multiplication: Distributive property = ac + ab = a (b + c) associative property = abc = a (bc).

Commutative law = ab = ba

Product invariant property = ab = (a c) (bc) (c≠0) addition: associative law = a + b + c = a + (b + c).

Commutative law = ab = ba

Easy Calculation:

1. Allocation method In parentheses is addition or subtraction operations, multiply with another number, pay attention to distribution.

Example: 45 (10+2)=45 10+45 2=450+90=5402, Extract Common Factor Pay attention to the extraction of the same factor.

Example: 35 78+22 35=35 (78+22)=35 100=3500 Here 35 is the same factor.

3. Pay attention to the structure, so that the equation satisfies the law of multiplication and distribution.

conditions. Example: 45 99+45=45 99+45 1=45 (99+1)=45 100=4500

1. The single digit is "1"。

Quick calculation: head multiplication of the head of the head such as the head of the head of the head of the head of

2. The ten digits are "1".

Quick calculation formula: the head is 1, the tail is added as, and the tail is multiplied by the tail (more than 10 to be carried).

3. The single digit is "9"。

Quick formula: add 1 to each head, multiply and multiply by 10, subtract the additive, and finally put 1.

4. The ten digits are all "9".

5. The head is the same, and the tail is complementary (the mantissa adds up to 10).

Quick calculation formula: the head multiplies the head by 1, and the tail multiplies the tail by 2 places.

6. The head is complementary and the tail is the same.

Quick calculation formula: head by head by tail, tail by tail occupy 2 places.

7. Multiply the number of complementary numbers.

Quick calculation formula: the head plus 1 and then multiply the head, the tail multiplies the tail by 2 8, one of which is 11.

Quick calculation formula: don't move from beginning to end, add and put in the middle.

8. Carry addition of two digits plus two digits.

Formula: Add 9 to subtract 1, add 8 to subtract 2, add 7 to subtract 3, add 6 to subtract 4, add 5 to subtract 5, add 4 to subtract 6, add 3 to subtract 7, add 2 to subtract 8, add 1 to subtract 9. Note: The number of additions in the formula is the number in the single digit.

9. Abdication subtraction of two digits minus two digits.

Verbal decision: minus 9 to add 1, minus 8 to add 2, minus 7 to add 3, minus 6 to add 4, minus 5 to add 5, minus 4 to add 6, minus 3 to add 7, minus 2 to add 8, minus 1 to add 9.

Grade 3 Introduction] Oral arithmetic is one of the teaching methods of mathematics. A method of calculation based solely on thinking and verbal activities without borrowing any tools. It develops students' ability to calculate quickly and develops their attention, memory and thinking skills.

After proficiency in oral arithmetic, there are socks to stop the pen to help the written arithmetic, and it is easy to apply in daily life. The following is the relevant information of "Oral Arithmetic Questions for Third Grade Primary School Students" compiled by the test network, I hope to help you.

Oral arithmetic problems for third-grade primary school students Part 134 20= 33 30= 31 20= 700 6= 84 10= 9 800=

38-7+69= 4 1 9= 84+42 6= 91-37+58= 2 7-0= 89+93-26=

Oral arithmetic questions for third-grade primary school students Part 2Oral Mathematics Questions for Grade 3 Primary School Students

There are three methods of math quick oral arithmetic.

1.Make use of the Shoten method.

If there are two numbers in the equation or if the numbers are added together to get ten, then you can make up ten by inverting the order of the numbers. For example, 13+8+7, we can swap the positions of 8 and 7, first calculate 13+7, and then add 8 to get the final answer. Doing so can lead to quick answers, improving computational efficiency and accuracy.

The operation of the method of making up ten is the same in subtraction, first add the minus numbers that can make up 10, and then subtract the subtracted number to get the answer.

2.Use the integer method.

It is to treat numbers close to 10, close to 100, and close to 1000 as integers, and then add and subtract them. For example, when solving the question of 397+123, we can think of 397 as 400, and then use 400+123 to get the answer as 523, and finally subtract 3 to get the final answer to 520. The same can be used for subtraction, as well as in the way of operation.

3.Use the displacement method.

Shift the numbers in the equation along with the previous symbols, and then calculate. This is a method that can often be used in primary school mathematics oral arithmetic, such as 3-4+5, many children do not know how, think that 3 can not be subtracted from 4, in fact, we move 5 together with the previous + sign, and transform it into 3+5-4, you can quickly get the answer.

2. Fill in the blanks. ( square centimeters = 1500 square decimeters = ( square meters.)

Year = ( Quarter = ( Month

The product of the two digits and the smallest three digits is ( ) It is estimated that it is about ( ) 4 kg of apples are sold for 10 yuan, and the unit price is ( ).

The rectangular area is 90 square meters, 15 meters long, and the perimeter ( ) three, judgment. The circumference of the two squares is not equal, and the area may be equal. (The area of a square with a side length of 1 cm is 1 square decimeter.) (

The commonly used units of length are square jujube centimeters, square decimeters, and square meters. (2000 is a leap year.) 4. Calculations.

Calculation: 5. Columnar calculation. What is 480?

What is the quotient of 40 and 30 divided by 420?

What is the quotient of the sum of 75 and 25 divided by the difference between the brothers?

6. Practical questions.

A rope is 120 meters long, first fold it in half and cut it once, and then divide each section into three equal parts, how many meters is each part long? (Solve in two ways).

3 ducks weigh 14 kilograms, so how many kilograms do 12 ducks weigh?

The square is 12 meters long, how many rectangles with an area of 6 square decimeters can be cut from it?