Math 2 Lesson: 9 plus a number: 9 +5

### 1.1. Knowledge to remember

– Grasp the table to add 9 with a number.

– In an addition operation, if the positions of two numbers are changed, the result of that calculation does not change.

### 1.2. Math forms

**Form 1: Performing the calculation**

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

– Perform the addition of the numbers of each row in order from right to left.

**Form 2: Mental calculation**

– Calculate the sum of numbers with a value of 10

– Calculate with the remaining numbers.

**Form 3: Math Quiz**

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

– Find a solution: When the problem requires finding the value of “both” or “all”, I often use addition.

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

– Check the solution of the problem and the result you just found?

### 1.3. Solving Textbook Exercises

**Lesson 1**

Mental arithmetic:

9 + 3 = 9 + 6 = 9 + 8 = 9 + 7 = 9 + 4 =

3 + 9 = 6 + 9 = 8 + 9 = 7 + 9 = 4 + 9 =

__Solution method__

Add the numbers and fill in the blanks with the result.

__Solution guide__

9 + 3 = 12 9 + 6 = 15 9 + 8 = 17 9 + 7 = 16 9 + 4 = 13

3 + 9 = 12 6 + 9 = 15 8 + 9 = 17 7 + 9 = 16 4 + 9 = 13

Lesson 2

Calculate:

__Solution method__

Add the numbers and fill in the blanks with the result.

__Solution guide__

lesson 3

Calculate:

9 + 6 + 3 = 9 + 4 + 2 =

9 + 9 + 1 = 9 + 2 + 4 =

__Solution method__

Perform calculations in order from left to right.

__Solution guide__

9 + 6 + 3 = 18 9 + 4 + 2 = 15

9 + 9 + 1 = 19 9 + 2 + 4 = 15

Lesson 4

In the garden there are 9 apple trees, mother planted 6 more apple trees. How many apple trees are there in the garden?

__Solution method__

**Summary**

There are: 9 apple trees cây

Extra : 6 apple trees

All have: … apple tree?

**The answer**

To find the solution, we take the original number of apple trees plus the number of additional apple trees.

__Solution guide__

The total number of apple trees in the garden is:

9 + 6 = 15 (apple tree)

Answer: 15 apple trees.

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