11 minus a number: 11-5

### 1.1. Knowledge to remember

Set and calculate: 11 – 5

1 cannot subtract 5, take 11 minus 5 equals 6, write 6, remember 1.

1 minus 1 equals 0

So 11 – 5 = 6

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

2 + 9 = 3 + 8 = 4 + 7 = 5 + 6 =

11 – 9 = 11 – 8 = 11 – 7 = 11 – 6 =

11 – 2 = 11 – 3 = 11 – 4 = 11 – 5 =

b) 11 – 1 – 5 = 11 – 1 – 9 = 11 – 1 – 3 =

11 – 6 = 11 – 10 = 11 – 4 =

__Solution method__

Mentally the results of additions; subtract 11 with a number and fill in the blank with the result.

__Solution guide__

a) 9 + 2 = 11 8 + 3 = 11 7 + 4 = 11 6 + 5 = 11

2 + 9 = 11 3 + 8 = 11 4 + 7 = 11 5 + 6 = 11

11 – 9 = 2 11 – 8 = 3 11 – 7 = 4 11 – 6 = 5

11 – 2 = 9 11 – 3 = 8 11 – 4 = 7 11 – 5 = 6

b) 11 – 1 – 5 = 5 11 – 1 – 9 = 1 11 – 1 – 3 = 7

11 – 6 = 5 11 – 10 = 1 11 – 4 = 7

Lesson 2

Calculate:

__Solution method__

Perform the subtraction 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) 11 and 7; b) 11 and 9; c) 11 and 3.

__Solution method__

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

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

__Solution guide__

Lesson 4

Vase has 11 balloons, Binh gives you 4 balls. How many balloons does Binh have left?

__Solution method__

To find the number of balloons left, we subtract the number of balls we had initially.

__Solution guide__

The number of balloons left in the jar is:

11 – 4 = 7 (ball)

Answer: 7 balloons.

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