14 minus a number: 14-8

### 1.1. Knowledge to remember

### 1.2. Math forms

**Form 1: Calculate**

– Set alignment.

– Perform subtraction in turn from right to left, when the unit row of the number being subtracted is not enough to subtract, you need to perform the subtraction with memory.

**Form 2: Build the math and find the result.**

– Write calculations according to the data of the given problem.

– Perform calculations to find the value of the result.

**Form 3: Math Quiz**

– Read and analyze the topic

– Find the solution of the problem: Pay attention to the keywords “all”; “remaining”… to use appropriate math in solving problems.

– Presentation of the problem.

– Check the solution and the results you just found.

### 1.3. Solving Textbook Exercises

**Lesson 1**

Mental arithmetic:

a) 9 + 5 = 8 + 6 = 7 + 7 =

5 + 9 = 6 + 8 = 14 – 7 =

14 – 9 = 14 – 8 = 14 – 4 =

14 – 5 = 14 – 6 = 14 – 10 =

b) 14 – 4 – 2 = 14 – 4 – 5 = 14 – 4 – 1 =

14 – 6 = 14 – 9 = 14 – 5 =

__Solution method__

a) Mentally calculate mathematical operations and fill in the blanks with the results.

b) Subtract the numbers from left to right.

__Solution guide__

a) 9 + 5 = 14 8 + 6 = 14 7 + 7 = 14

5 + 9 = 14 6 + 8 = 14 14 – 7 = 7

14 – 9 = 5 14 – 8 = 6 14 – 4 = 10

14 – 5 = 9 14 – 6 = 8 14 – 10 = 4

b) 14 – 4 – 2 = 8 14 – 4 – 5 = 5 14 – 4 – 1 = 9

14 – 6 = 8 14 – 9 = 5 14 – 5 = 9

**Lesson 2**

Calculate:

__Solution method__

Perform subtraction 14 with a number and then fill in the blank with the result.

__Solution guide__

**lesson 3**

Set the calculation and then calculate the difference, knowing the subtracted and subtracted numbers are:

a) 14 and 5; c) 14 and 7; c) 12 and 9.

__Solution method__

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

– Calculate: Perform subtraction and then fill in the blank with the result.

__Solution guide__

**Lesson 4**

A store with 14 electric fans sold 6 electric fans. How many electric fans are left in that store?

__Solution method__

To find the remaining number of electric fans, we take the number of electric fans the shop had at the beginning minus the number of electric fans sold.

__Solution guide__

That store has the remaining electric fans:

14 – 6 = 8 (electric fan)

Answer: 8 electric fans.

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