1, fractional multiplication: the meaning of fractional multiplication is the same as integer multiplication, and it is a simple operation to find the sum of several identical addends.

2. Calculation rules of fractional multiplication

Fractions are multiplied by integers, and the product of the multiplication of fractions and integers is a numerator, and the denominator remains unchanged; Fractions are multiplied by fractions, the product of numerator multiplication is numerator, and the product of denominator multiplication is denominator. But numerator and denominator cannot be zero.

3. The importance of fractional multiplication

Fractional multiplication of integers, like integer multiplication, is a simple operation to find the sum of several identical addends. Multiplying a number by a fraction can be regarded as finding a fraction of this number.

4. Fraction multiplied by integer: combination of numbers and shapes, and conversion.

5. Reciprocal: Two numbers whose product is 1 are called reciprocal.

6, the reciprocal of the score

Find the reciprocal of the fraction, such as 3/4. Switch 3/4 numerator and denominator, so that the original numerator and denominator are the same. It's four-thirds. 3/4 is the reciprocal of 4/3, or 4/3 is the reciprocal of 3/4.

7, the reciprocal of an integer

Find the reciprocal of an integer, such as 12, divide 12 into several components, namely 12/ 1, and then exchange the numerator and denominator of the fraction of 12/ 1 with the original numerator as the denominator. Is112,12 is the reciprocal of112.

8. Ordinary algorithm for reciprocal decimal: Find the reciprocal of a decimal, such as 0.25, divide 0.25 into several components, namely 1/4, and then exchange the numerator and denominator of the fraction of 1/4, with the original numerator as the denominator and the original denominator as the numerator. It is 4/ 1.

9. Calculate by 1: You can also divide this number by 1, for example, 0.25, 1/0.25 equals 4, then the reciprocal of 0.25 is 4, because the product is the reciprocal of 1. Fractions and integers also use this law.

10, fractional division: fractional division is the inverse of fractional multiplication.

1 1, the calculation rule of fractional division: A divided by B (except 0) equals the reciprocal of A multiplied by B.

12, the meaning of fractional division is the same as that of integer division, that is, the product of two factors is known and one of them is used to find the other factor.

13, fractional division problem: find the unit first 1. Known unit 1. Multiplication is used to find partial quantity or corresponding fraction, and division is used to find unit 1.

14, ratio and proportional ratio and proportional ratio have always been one of the most confusing problems in mathematics. In fact, the problem between the two can be summarized in one sentence: the ratio is equivalent to the formula on the left of the equal sign in the formula and is one of the formulas; Proportion is formed by connecting at least two formulas called ratio by an equal sign, and the ratio of these two ratios is the same.

So the relationship between ratio and proportion can be said as follows: ratio is a part of proportion; The ratio consists of at least two ratios with equal ratios. Two expressions with equal ratios are called ratios, which means ratios. There are four proportions, two in the front and two in the back.

15, the basic properties of the ratio: the first term and the second term of the ratio are multiplied or divided by a non-zero number. This ratio remains unchanged. The nature of the ratio is used to simplify the ratio. The ratio represents the division of two numbers; There are only two items: the first item and the last item of the ratio. Proportion is an equation, which means that two proportions are equal; There are four projects: two external projects and two internal projects.