Subtraction within 8

### 1.1. Knowledge to remember

– How to do subtraction within 8

– Represent the situation in the figure by calculation and application of subtraction just learned to real problems.

### 1.2. Maths for Subtraction within 8

**Form 1: Performing the calculation**

Calculate the value of subtractions within 8.

**Type 2: Calculates the value of an expression containing multiple addition and subtraction operations phép**

If an expression contains two or more addition and subtraction operations, you perform the calculations from left to right.

**Form 3: Fill in the missing element in the calculation**

Repeat the learned addition and subtraction of numbers within 8 and then fill in the missing numbers or signs in the blanks.

### 1.3. Solve textbook exercises pages 73, 74

**Lesson 1 page 73**

Calculate:

**Solution method**

Perform vertical subtraction of numbers and then write the result in the blank.

__Solution guide__

**Lesson 2 page 73**

Calculate:

1 + 7 = 2 + 6 = 4 + 4 =

8 – 1 = 8 – 2 = 8 – 4 =

8 – 7 = 8 – 6 = 8 – 8 =

__Solution method__

Perform calculations with numbers and then write the results in the blanks.

__Solution guide__

1 + 7 = 8 2 + 6 = 8 4 + 4 = 8

8 – 1 = 7 8 – 2 = 6 8 – 4 = 4

8 – 7 = 1 8 – 6 = 2 8 – 8 = 0

**Lesson 3 page 74**

Calculate:

8 – 4 = 8 – 5 = 8 – 8 =

8 – 1 – 3 = 8 – 2 – 3 = 8 – 0 =

8 – 2 – 2 = 8 – 1 – 4 = 8 + 0 =

__Solution method__

Subtract the numbers from left to right and then fill in the blank with the result.

__Solution guide__

8 – 4 = 4 8 – 5 = 3 8 – 8 = 0

8 – 1 – 3 = 4 8 – 2 – 3 = 3 8 – 0 = 8

8 – 2 – 2 = 4 8 – 1 – 4 = 3 8 + 0 = 8

**Lesson 4 page 74**

Write the appropriate calculation:

__Solution method__

Count the number of fruits, the number of fruits crossed out and then write the appropriate calculation.

**Solution guide**

### 1.4. Textbook Exercises Page 75

**Lesson 1 page 75**

Calculate:

7 +1 = 6 + 2 = 5 + 3 = 4 + 4 =

1 + 7 = 2 + 6 = 3 + 5 = 8 – 4 =

8 – 7 = 8 – 6 = 8 – 5 = 8 + 0 =

8 – 1 = 8 – 2 = 8 – 3 = 8 – 0 =

**Solution method**

Calculate the value of the operations and then write the results in the blanks

**Solution guide**

7 +1 = 8 6 + 2 = 8 5 + 3 = 8 4 + 4 = 8

1 + 7 = 8 2 + 6 = 8 3 + 5 = 8 8 – 4 = 4

8 – 7 = 1 8 – 6 = 2 8 – 5 = 3 8 + 0 = 8

8 – 1 = 7 8 – 2 = 6 8 – 3 = 5 8 – 0 = 8

**Lesson 2 page 75**

Number?

**Solution method**

Perform the calculation and then fill in the blank with the result.

**Solution guide**

**Lesson 3 page 75**

Calculate:

4 + 3 + 1 = 8 – 4 – 2 = 2 + 6 – 5 = 8 + 0 – 5 =

5 + 1 + 2 = 8 – 6 + 3 = 7 – 3 + 4 = 3 + 3 – 4 =

**Solution method**

Add or subtract numbers in order from left to right and write the result in the blank.

**Solution guide**

4 + 3 + 1 = 8; 8 – 4 – 2 = 2;

5 + 1 + 2 = 8; 8 – 6 + 3 = 5;

2 + 6 – 5 = 3; 8 + 0 – 5 = 3

7 – 3 + 4 = 8; 3 + 3 – 4 = 2

**Lesson 4 page 75**

Write the appropriate calculation

**Solution method**

– Count the number of apples, the number of apples outside and the number of apples left in the basket.

– Write the appropriate calculation.

**Solution guide**

The calculation is: 8 – 2 = 6.

**Lesson 5 page 75**

Match the blank cells with the appropriate number:

**Solution method**

– Calculates the value of the given calculations.

– Match the given number with the appropriate blank, so that the number satisfies the required problem condition.

**Solution guide**

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