I. Fractional multiplication

(A) the significance of fractional multiplication:

1, fractional multiplication by integer has the same meaning as integer multiplication. Is a simple operation to find the sum of several identical addends.

For example, what is the sum of five when x 5 means?

2. the score multiplied by the score is to find the score of a number.

For example, × indicates what the solution is.

(2), the calculation rules of fractional multiplication:

1, Fraction multiplied by integer: the product of numerator multiplied by integer is numerator, and the denominator remains unchanged. (Integer and denominator divisor)

2. Fraction and fractional multiplication: use the product of molecular multiplication as the numerator and the product of denominator multiplication as the denominator.

3. In order to simplify the calculation, the points that can be reduced are reduced first and then calculated.

Note: When multiplying with a fraction, the fraction should be converted into a false fraction before calculation.

(3) Law: (When the multiplication is relatively large)

A number (except 0) is multiplied by a number greater than 1, and the product is greater than this number.

A number (except 0) multiplied by a number (except 0) is less than 1, and the product is less than this number.

A number (except 0) is multiplied by 1, and the product is equal to this number.

(4) The operation order of fractional mixed operation is the same as that of integer.

(5) The commutative law, associative law and distributive law of integer multiplication are also applicable to fractional multiplication.

Multiplicative commutative law: a×b=b×a

Law of multiplicative association: (a×b)×c=a×(b×c)

Multiplication and distribution law: (a+b)×c=ac+bc.

Second, solve the problem of fractional multiplication.

(The quantity (times) of a given unit 1 is a fraction of the unit 1? )

1, draw a line chart:

(1) The relationship between two quantities: draw two line segments; (2) The relationship between the part and the whole: draw a line segment.

2. Find the unit 1: before the rate in the rate sentence; Or the back, yes, than.

3. Find several times a number: a number × several times; Find the fraction of a number: a number ×.

4, write quantitative relationship skills:

(1) is equivalent to × accounting, yes, the ratio is equivalent to =

(2) Before the score is: unit 1 × number of scores = number corresponding to the score.

(3) Before the score, it means more or less: unit 1 ×( 1 score) = the amount corresponding to the score.

Third, the countdown.

The meaning of 1 and reciprocal: two numbers whose product is 1 are reciprocal.

Emphasis: reciprocal, that is, reciprocal is the relationship between two numbers. They are interdependent and reciprocity cannot exist alone.

Find out who is the reciprocal of who.

2. Reciprocal method:

(1), find the reciprocal of the fraction: exchange the position of the denominator of the numerator.

(2) Find the reciprocal of an integer: treat an integer as a fraction with a denominator of 1, and then exchange the positions of the denominator of the numerator.

(3) Find the reciprocal of the band score: turn the band score into a false score, and then find the reciprocal.

(4) Find the reciprocal of decimals: Turn decimals into fractions, and then find the reciprocal.

3. The reciprocal of1is1; 0 has no reciprocal. Because/kloc-0 /×1=1; Multiply 0 by any number to get 0 (denominator cannot be 0).

4. For any number, its reciprocal is; The reciprocal of a nonzero integer is; The reciprocal of the score is;

5. The reciprocal of the true score is greater than1; The reciprocal of the false score is less than or equal to1; The reciprocal of the score is less than 1.