"Multiplication of Rational Numbers" Rational Numbers and Their Operations PPT Courseware

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"Multiplication of Rational Numbers" Rational Numbers and Their Operations PPT Courseware

The water level in Reservoir A rises by 3 centimeters per day, and the water level in Reservoir B drops by 3 centimeters per day. What is the total change in the water levels in Reservoir A and Reservoir B after 4 days?

If a positive sign indicates an increase in water level and a negative sign indicates a decrease in water level, then the water level change in Reservoir A after 4 days is: 3＋3＋3＋3＝3×4＝12 (cm)

In the same way: the water level change of reservoir B is:

(-3) + (-3) + (-3) + (-3) = (-3) × 4 =?

Types of rational multiplication:

1. Positive number × positive number

2. Negative number × negative number

3. Positive number × negative number

4. Negative number × positive number

5. 0 × positive number

6. 0 × negative number

The five examples are summarized below:

(1)2×3=6

(2)(-2)×(-3)=6

(3)(-2)×3=-6

(4)2×(-3)=-6

(5) When the multiplicand or multiplier is 0, the result is 0

Multiplying with the same sign, the product is a positive number

Multiplying with different signs, the product is negative

Rational number multiplication rule: when two numbers are multiplied, if they have the same sign, they will be positive, if they have different signs, they will be negative, and the absolute values ​​will be multiplied together. Any number multiplied by 0 gets 0.

Notice:

a. When a number is multiplied by +1, the original number is obtained. When a number is multiplied by -1, the opposite of the original number is obtained.

b. Two rational numbers whose product is 1 are reciprocals of each other.

summary:

1. Rules for multiplication of rational numbers:

When two numbers are multiplied together, the numbers with the same sign will be positive, and the numbers with different signs will be negative. If the absolute values ​​are multiplied together, any number multiplied by 0 will get 0.

2. How to perform operations on two rational numbers:

First determine the sign of the product, and then multiply the absolute values. When one factor is zero, the product is zero.

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Update Time: 2024-09-24

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