Math 2 Lesson: Numbers

### 1.1. Knowledge to remember

– Know the position and name of terms and sums in an addition.

– Perform addition without memory within 100 and apply it to solving puzzles

**Attention:** 35 + 24 is also called the sum.

### 1.2. Math forms

**Type 1: Perform the calculation.**

– Set in vertical columns, numbers in the same row are placed straight together.

– Add numbers from units to tens.

**Form 2: Math quizzes**

– Read and analyze the problem: Determine the given data, the amount of increase or decrease and the requirements of the problem.

– Find a solution: Based on the key words of the problem such as finding “all”, “remaining” … and the requirements of the problem to determine the appropriate calculation.

– Presentation of the solution: Write the solution, calculation and answer to the problem.

– Check the solution of the problem and the results just found.

**Form 3: Find the missing digit in the addition calculation.**

– Perform addition from units to tens.

– The addition operation has three values: the first term, the second term, and the sum. If I know the value of two of those three values, I will mentally find the missing numeric value.

### 1.3. Solve textbook exercises page 5

**Lesson 1**

Write the correct number in the blank (follow the pattern):

__Solution method__

Perform the addition of two numbers in order from units to tens.

__Solution guide__

**Lesson 2**

Set calculation and then sum (in the form), know:

a) The terms are 42 and 36

b) The terms are 53 and 22

c) The terms are 30 and 28

d) The terms are 9 and 20

__Solution method__

Do the calculation according to the pattern.

– Set calculation: Write the digits in the same row and column together.

– Calculation: Add the digits from right to left.

__Solution guide__

**lesson 3**

A shop sells 12 bicycles in the morning and 20 in the afternoon. How many bicycles did the store sell in two sessions?

__Solution method__

*Summary*

Morning sale: 12 bikes

Afternoon sale: 20 bikes

Full day sale: ….. bike?

**The answer:**

To find the number of bicycles sold all day, we need to add the number of bicycles sold in the morning plus the number of bicycles sold in the afternoon.

__Solution guide__

Two times the shop sold all the bicycles:

12 + 20 = 32 (bike)

Answer: 32 bicycles.

### 1.4. Solve textbook exercises page 6

**Lesson 1**

Calculate:

__Solution method__

Perform addition of numbers from right to left.

__Solution guide__

**Lesson 2**

Mental arithmetic:

50 + 10 + 20 =

60 + 20 + 10 =

40 + 10 + 10 =

50 + 30 =

60 + 30 =

40 + 20 =

__Solution method__

Add up the digits of the tens place mentally and then add a 0 to the end of the result you just found.

__Solution guide__

50 + 10 + 20 = 80

60 + 20 + 10 = 90

40 + 10 + 10 = 60

50 + 30 = 80

60 + 30 = 90

40 + 20 = 60

**lesson 3**

Set the calculation and then sum, knowing the terms are:

a) 43 and 25; b) 20 and 68; c) 5 and 21

__Solution method__

– Set the calculation: Write the calculation in a vertical row so that the digits in the same row and column are together.

– Calculation: Add the numbers in order from right to left.

__Solution guide__

a)

b)

c)

In the library, there are 25 boys and 32 girls. How many students are in the library altogether?

__Solution method__

**Summary**

Male students: 25 students

Female students: 32 students học

All of students?

**The answer:**

To find all the students in the library, add the number of boys plus the number of girls.

__Solution guide__

The number of students in the library is:

25 + 32 = 57 (student)

Answer: 57 students.

**Lesson 5**

Fill in the blanks with the correct number:

__Solution method__

Repeat from right to left to find the missing number.

__Solution guide__

.

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