"Multiplication of Rational Numbers" Rational Numbers and Their Operations PPT Courseware (Lesson 2)

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"Multiplication of Rational Numbers" Rational Numbers and Their Operations PPT Courseware (Lesson 2)

Part One: Learning Objectives

1. Master the distributive law of multiplication and be able to use it flexibly. (Difficulty)

2. Master the operational laws of rational number multiplication, and use the operational laws to simplify multiplication operations. (Key points)

Multiplication of rational numbers PPT, part 2: introducing new lessons

Problem introduction

In primary school, we all know that the multiplication of numbers satisfies the commutative, associative and distributive laws, for example

3×5=5×3

(3×5)×2=3×(5×2)

3×(5+2)=3×5+3×2

After introducing negative numbers, do the three laws of operation still hold?

Multiplication of rational numbers PPT, part 3: teaching new lessons

Arithmetic laws of multiplication of rational numbers

collaborative inquiry

First group:

(1) 2×3＝ 3×2＝

(2) (3×4)×0.25＝ 3×(4×0.25)＝

(3) 2×(3+4)＝ 2×3+2×4＝

Thinking: What operational laws are reflected in each group of operations above?

in conclusion:

(1)The range of numbers in the first set of formulas is ________;

(2)The range of numbers in the second set of formulas is ________;

(3) Comparing the formulas in the first group and the second group, we can find _______________________________.

In conclusion

1. Commutative law of multiplication:

When two numbers are multiplied together, the positions of the two factors are swapped, and the products are equal.

ab＝ba

2. Associative law of multiplication:

To multiply three numbers, first multiply the first two numbers, or multiply the last two numbers first, and the products will be equal.

(ab)c = a(bc)

According to the commutative law of multiplication and the associative law, it can be deduced:

When multiplying three or more rational numbers, the positions of the factors can be exchanged arbitrarily, or several of the numbers can be multiplied first.

3. The distributive law of multiplication to addition:

Multiplying a number by the sum of two numbers is equivalent to multiplying the number by the sum of the two numbers and then adding the products.

According to the distributive law, it can be deduced:

Multiplying a number by the sum of several numbers is equivalent to multiplying the number by the sum of several numbers and then adding the products.

Multiplication of rational numbers PPT, part 4: practice in class

1. The formula -25×14+18×14-39×(-14)=(-25+18+39)×14 is used inversely ()

A. Commutative law of addition B. commutative law of multiplication

C． Multiplicative associative law D. The distributive law of multiplication versus addition

3. Calculate:

(1)(-2.5)×0.37×1.25×(-4)×(-8)=_____;

Multiplication of rational numbers PPT, Part 5: Class summary

Laws of rational number arithmetic:

Commutative law of addition a+b=b+a

Additive associative law (a+b)+c=a+(b+c)

Commutative law of multiplication ab=ba

Multiplicative associative law (ab)c=a(bc)

The distributive law of multiplication to addition a(b+c)=ab+ac

Keywords: Beijing Normal University edition seventh-grade mathematics PPT courseware free download, multiplication of rational numbers PPT download, rational numbers and their operations PPT download, .PPT format;

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Update Time: 2024-10-19

This template belongs to Mathematics courseware Beijing Normal University Edition Seventh Grade Mathematics Volume 1 industry PPT template

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