"Rational Numbers" PPT Courseware 5

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"Rational Numbers" PPT Courseware 5

Review and review:

What did we talk about rational numbers in elementary school?

1. Positive and negative numbers.

2,0 is neither a positive number nor a negative number.

3. Positive numbers and negative numbers are usually used to represent quantities with opposite meanings.

4. What “0” means.

5. In production, positive and negative numbers are usually used to express the allowable error;

Review the past and learn the new:

1. If the length of the bicycle strip is 2mm longer than the standard length, it is recorded as +2mm. If it is 1.5mm shorter than the standard length, it should be recorded as ________.

2. The standard weight of each bag of grain is 50 kilograms. First, measure the weight of three bags of grain A, B, and C as follows: 52 kilograms, 49 kilograms, and 49.8 kilograms. If the overweight part is expressed as a positive number, please record A with positive and negative numbers. The overweight and underweight amounts of three bags of grain B, B and C;

3. The ITTF uses ball balls in official competitions and has strict standards for the diameter of large balls. There are currently 5 table tennis balls. Measure their diameters. The number of millimeters exceeding the standard is recorded as a positive number, and the number of millimeters that are insufficient is recorded as a negative number. The measurement results are as follows:

A.-0.1mm B.-0.2mm C.+0.25mm D.-0.05mm E.+0.15mm

Which table tennis ball do you think should be chosen for the game? Why?

Explore the classification of rational numbers (1)

It can be seen from the demonstration just now:

1. What two types of numbers can rational numbers be divided into?

2.What categories can integers be divided into?

3.What categories can scores be divided into?

Classification of rational numbers:

Note: We regard finite decimals, infinitely repeating decimals and percentages as fractions, but not all decimals are fractions. (Pi is an infinite non-repeating decimal, it cannot be converted into fractions)

Explore the classification of rational numbers (2)

1. Among the rational numbers in the picture on the left,

Positive integers include: ________;

Negative fractions include: ____________________;

The integers are: ____________________;

The scores are: ____________________.

2. When Dandan was doing question 1, she discovered a new classification method. She thought: numbers with "+" are divided into one category, numbers with "-" are divided into another category, and numbers without symbols in front of them are classified into one category. Category 1. Do you think her classification method is correct? If not, have you found any new classification methods?

practice

Answer the questions based on life situations:

① When the night sky is filled with stars, Little Beibei is counting the stars. What number does he use?

A positive number

②What types of rational numbers can be read on a measuring scale?

Positive numbers, fractions, zero

③A thermometer is used to measure the temperature. What types of rational numbers can be read from it?

Positive numbers, zero, negative numbers

summary:

1. What are rational numbers?

2. Classification of rational numbers:

(1) Divide by integers and fractions;

(2) Classification by nature;

3. How to distinguish integers and fractions?

4. How to understand non-positive numbers and non-negative numbers?

5. What is the relationship between integers and fractions, positive numbers and negative numbers?

6. Learn to observe the patterns between a series of numbers;

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Update Time: 2024-07-03

This template belongs to Mathematics courseware Qingdao Edition Seventh Grade Mathematics Volume 1 industry PPT template

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