"Using Letters to Represent Numbers" PPT Courseware

Description

"Using Letters to Represent Numbers" PPT Courseware

children's songs

1 frog has 1 mouth, 2 eyes and 4 legs, and jumps into the water with a plop;

2 frogs with 2 mouths, 4 eyes and 8 legs jumped into the water with 2 plop, plop sounds;

3 frogs with 3 mouths, 6 eyes and 12 legs jumped into the water with 3 sounds of plop, plop, plop;

Do you think this song can be finished?

How would this children's song be sung if there were more frogs?

n frogs have n mouths, 2×n eyes, 4×n legs, and jump into the water with n plops.

Using letters to represent numbers can express the relationship between numbers and quantities in a general and concise way.

Explore new knowledge

(1) The unit price of an exercise book is a yuan, and the total price of 100 exercise books is ________ yuan.

"To multiply numbers and letters, you can omit the multiplication sign and write the numbers in front of the letters."

(2) The unit price of the exercise book is a yuan, and the total price of the exercise book b is ________ yuan.

When multiplying letters by letters, the multiplication sign can be omitted or expressed with "·".

(3) The unit price of exercise books is 0.5 yuan, and the unit price of ballpoint pens is 3.2 yuan. The total price of buying exercise book a and pen b is ___________ yuan.

Addition or subtraction expressions with units at the end should be enclosed in parentheses.

※The writing format of expressing numbers using letters

When multiplying numbers and letters, when the multiplication sign is omitted, the numbers should be written in front of the letters. For example, n×2 should be written as 2n, not n2; when letters are multiplied by letters, the multiplication sign can be omitted or written with " ·". When multiplying numbers, you must use the multiplication sign "×"

Expressions for addition or subtraction followed by units should be enclosed in parentheses.

Division operations should be written in fraction form, with the division sign replaced by a fraction line.

When multiplying mixed numbers by letters, the mixed numbers should be written in the form of improper fractions

Review & Thoughts

Use letters to represent numbers to concisely express some mathematical rules:

(1) Use a and b to represent two numbers.

Commutative law of addition: a+b=b+a;

Commutative law of multiplication: ab=ba,

(2)a, b, c represent three numbers,

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

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

Distributive law: a(b+c) =ab+ac

practice

1. Xiao Ming is 14 years old this year. A year ago, Xiao Ming was ______ years old.

2. There are two consecutive natural numbers. The smaller one is n, and the larger one is ______.

3. Even numbers are represented by _______, and odd numbers are represented by ______.

4. It is known that the rational number a (a≠0), then the reciprocal of a is __＿,

The opposite of a is __, the absolute value of a is __,

The difference between a and -4 is __.

5. A two-digit number, each digit is a and the tens digit is b, then this number is ______.

Learning summary:

1. Letters can represent any number, operation rules, calculation formulas, quantitative relationships, change rules...

2. When multiplying numbers and letters, please note:

(1) The multiplication sign is usually omitted;

(2) Numbers are written before letters;

(3) Convert mixed numbers into improper fractions and write them before the letters;

(4) The formulas followed by the addition or subtraction of units must be in parentheses;

(5) Division operations are written in fraction form, and the division sign is changed to a fraction line.

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For more information about the PPT courseware "Using Letters to Represent Numbers", please click the Use Letters to Represent Numbers ppt tag.

"Review of Representing Numbers with Letters" PPT:

"Review of Using Letters to Represent Numbers" PPT Part One: Teaching Objectives 1. Review and organize the knowledge about using letters to express numbers in primary school. Through review, students can use letters to represent numbers in specific situations. Ability to use letters to represent operational rules and calculations..

"Using Letters to Represent Numbers" PPT:

"Representing Numbers with Letters" PPT Part One Content: Scenario introduction 1 frog 1 mouth 2 frogs 2 mouths 3 frogs 3 mouths.. N frogs ( ) mouths Example 1. Use expressions containing letters to express Yaya and Niuniu age relationship. When Niuniu was 1 year old, Yaya (1+3...

"Using Letters to Represent Numbers" PPT Courseware 7:

"Representing Numbers with Letters" PPT Courseware 7 The unit price of exercise books is a yuan. How to express the total price of 100 exercise books? Because the total price of exercise books = the number of exercise books x unit price, the total price of 100 exercise books is 100xa yuan is 100a yuan. Numbers are related to the letters that represent numbers...

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Update Time: 2024-10-29

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

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