Look at a large number, divide it into decimals, round it to ten, and add a fraction.

Master the "ten-point method" and advocate the "recursive method". )

Second, the subtraction of abdication within 20 years

Less than 20 abdicates, and the oral calculation method is simple.

Ten people return one, one person makes up, and the writing is accurate and fast.

Third, the meaning of addition, vertical calculation

When two numbers are added, the result of the addition is called sum.

Don't forget the numbers on the right, one for every ten.

Fourthly, the significance of vertical calculation subtraction.

Subtraction is used from big to small, and the result of subtraction is called difference.

Digital alignment starts from the right, and when it is not enough, take the front position.

Five, two-digit multiplication

Multiplication of two digits is not difficult. There are three points in the calculation process:

The multiplier must be calculated first and then multiplied by ten digits.

The last digit of the product is the key, which is opposite to the ten digits;

After the two products are added up, calculate the number of layers in your mind.

Six, two-digit division

Divide two by two, and two is not enough to divide three.

Except quotient, the remainder is less than divisor.

Then, except for the next item, the test method should be flexible.

Master the "rounding" method and the "same business comparison method".

Understand the semi-definite commercial law and divide the quotient by nine or eight. (where: same head, less high position 1)

Seven, mixed operation

Look at the formula carefully, calculate multiplication and division and add alkali.

When you encounter brackets, you should count them first, and the application rules should be changed.

There are some data to memorize and skills to master.

Eight, fast addition and subtraction

Add and subtract quickly, don't worry, you can see clearly when you get the formula.

Rounded integer close to the whole hundred, the following treatment is not fallacious.

If you don't add enough, you will reduce the complement and add the extra score to the end.

If the subtraction is insufficient, add the complement, and then subtract the excess score.

Nine, multi-digit reading method

The reading method is very simple. First, the fourth grade.

We should start from the highest place, thousands, hundreds, and ten.

Grade units read hundreds of millions, and no zeros are read at the end.

(Don't read the 0 at the end of the stage, and don't read the 0 at the end of the integer)

Read one with a zero in the middle, and the expression of Chinese characters is irrelevant.

Note that the reading is zero:

1, ten thousand levels, the first level has zero.

2, the whole class is zero.

There are zeros at the end of the superior and at the top of the subordinate.

4. There is a 0 in the middle of each level.

X. decimal addition and subtraction

Decimal addition and subtraction calculation problems, with point alignment.

An algorithm is like calculating an integer. After the calculation, move the point down.

XI。 Decimal multiplication

Decimals are multiplied by decimals in the same way as integers.

Fixed product decimal places, factors * * * together.

Twelve, divisor is the division of decimals

Divide the dash of the decimal point, (remove the decimal point)

Move the decimal point of dividend, move it to the right,

The number of decimal places of a divisor determines it.

Thirteen, prime songs

A prime number 2, 3, 5 and 7,

Add 1 before 1, 3, 7 and 9.

After 4, before 3 and 7, after 9 and 7, 1,

Add 7, 1 after 3, 4 and 6,

Add 9, 3 after 2, 5, 7 and 8,

Remember all 25 prime numbers.

Fourteen, fractional multiplication and division method

Fractional multiplication is easy to learn and understand, and numerator and denominator are multiplied separately. The meaning of the formula should be clear, and it is easier to make an appointment. Fractional division is wonderful, changing the original division symbol into multiplication symbol. The divisor is reversed, so calculation is essential.

Fifteen, about the point

Tangent point, tangent point, take the net, save time and effort. From top to bottom, from left to right, make the data clear and don't miss a number. When you encounter a decimal, the decimal point is an integer, and if the number of digits is not enough, use "zero" to make up.

Sixteen, the judgment of prime numbers

Fractional ratio simplification, both ends of prime number. Observe five points: 1 and all the numbers; Two adjacent numbers; The two qualities must be mutual. A large number is a prime number and two numbers are coprime. Decimals are prime numbers, and large numbers are not multiples. (It is a decimal)

Seventeen, the text questions

There are three narrative forms, meaning and name. Remember the method of solving problems clearly, and simplify sentences in one step. Punctuation does not delay the sense of hierarchy. There are two formulaic methods, which can be used as formulas and equations.

XVIII. Application of Comparative Relationship

(A) the phase difference relationship

1 is more or less a big reduction.

2. The proportion of known conditions is more, less than before.

3. The proportion of known conditions is small, and the proportion is reduced first and then increased.

(2) Multiple relationships

1 and time are separated in the problem.

2. Times Under known conditions, multiply before and divide after.

(3) Find a number that is more than (less than) several times.

Divide the multiplier by multiples and add and subtract by how many points.

Add and subtract after division and add and subtract after multiplication.

Nineteen. Looking for the unit "1"

The unit "1" is cleverly hidden, and I will find you according to the score.

"Among them," standing in front ",yes, accounts for more than" sitting in the back;

"Question and answer" can be found, and supplementary instructions should be done well.

Percentages are often encountered, so it is more polite not to use the word "rate".

Find a pair of good friends, and then determine the multiplication and division number.

Find the description of the cell "1":

Grasp the "key sentences" and "keywords" that contain scores but have no unit names for analysis, thus solving the problem that many students are confused about how to analyze the quantitative relationship. Therefore, letting students learn to quickly find "key sentences" and "keywords" to analyze the quantitative relationship can not only help them master the general law of solving fractional application problems, but also cultivate their ability and develop their intelligence. It is a common learning rule for sixth grade students to "find" first and then "analyze". Remember to guide students to analyze carefully and orderly.

Fractional application problem 1, find 2, understand 3, decide 4, and the corresponding problem-solving ideas.

Twenty, the application of positive and negative ratio

In direct proportion, it is divided into three sections, and the intermediate quantity remains unchanged.

Put them in separate columns and then connect them with an equal sign.

The inverse proportion is divided into three sections, and the constant is in the front.

"If" is divided into total columns and then connected by an equal sign.

Creative examples of using jingles:

The application problem of "finding more than one number"

In the fourth volume of the six-year mathematics textbook, we compare the two application problems of "finding a number greater than a number" and "finding a number less than a number" and get a difference. Knowing the difference between two numbers and one of them, finding another number means finding a number that is more or less than one. So "greater than …" and "less than …" are both inverse problems for finding the difference between two numbers, and the topic structure is the same. The application of "more" and "less" with known conditions is only two sides of the same problem. The most common mistake students make when solving this kind of problems is to add more when they see more, and subtract when they see less, and judge the algorithm by a single word. My teaching idea is: 1, analyze the quantitative relationship and teach students the method of thinking. 2. Give full play to the role of the line chart, so that the "thing" of the application problem can be transformed into "reason", and then the "reason" can be transformed into "formula" to express it intuitively, and then find out the law.

Example: P 17 Example 5 bright primary school planted 300 willows. There are 70 more poplars than willows. How many poplars have been planted?

1. Question: What kinds of trees are there? (willow, poplar)

Who is better than who? (Yang Liubi)

Who has more? Who is less (more poplars)? (Little willow)

2. Calculation formula: number of willows+number of poplars more than willows = number of poplars.

3. The formula is: 300+70=370 (tree)

4. If the first condition is changed to a question and the question is changed to a condition, how should it be calculated?

5. Then get the key sentences: there are more known conditions than before (the number of requirements is higher than before) and the number of requirements is lower than after. Solve the application problem of children's songs

Look at the topic several times to find the key points;

Look at what you want first, and then find conditions;

Reasonable calculation formula, careful calculation;

Ask for more answers to a question, and the unit will not forget it;

Check the results and finally write the answer.

Round nursery rhymes

The rounding method is good, and the approximate figure can be found out by law;

Take which one to look at the next one, and then compare it with five words;

It is 5 big 5 forward 1, and all less than 5 are discarded;

The equal sign is replaced by an equal sign, which makes people understand at a glance.

Length unit identification song

1 cm, very naughty, look carefully before you look.

Nail cover 1 cm, stretch out your finger and compare it.

It's about my length, about one centimeter.

100 I'm 1 m, and I'm Mi's little brother.

Don't use me when the object grows, or you will be exhausted.

A divisor is the division of a single digit.

One point one, one point two, (one point one)

Except for which dealer, (two vendors and three times less)

Divider is the division of two digits.

See two in two, two is not enough to see three.

Except which business, remember the formula and make a reservation.

The trial commercial law should be flexible, and the quotient "1" and "0" are not enough.

The remainder is less than the divisor and then divided by the next bit.

Divide by the number and be a sister. (More than four to five)

The operation order of elementary arithmetic is the first place in parentheses, followed by multiplication and division, and then addition and subtraction. Whoever comes first counts first.