Math 2 Lesson: Subtracted Numbers – Subtracted Numbers

### 1.1. Knowledge to remember

**Attention:** 59 – 35 also called brand

– Memorize the name and position of the number to be subtracted, the number of subtraction and the difference in subtraction.

– How to perform non-remember subtraction in the range \(100\) and apply it to solving problems

### 1.2. Math forms

**Type 1: Perform the calculation.**

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

– Perform subtraction in order 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: Mental calculation**

Perform subtraction of round numbers without setting calculation.

– I subtract the digits in the tens

– Add a digit 0 . to the result

### 1.3. Solve the textbook exercises page 9

**Lesson 1**

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

__Solution method__

Perform subtraction from right to left.

__Solution guide__

Lesson 2

Set the calculation and then calculate (according to the form), know:

a) The subtracted number is 79, the minus number is 25

b) The minus number is 38, the minus number is 12

c) The subtracted number is 67, the minus number is 33

d) The subtracted number is 55, the minus number is 22.

__Solution method__

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

– Perform subtraction from right to left in turn.

__Solution guide__

lesson 3

A rope is 8dm long, cut a length of 3dm. How many decimeters is the length of the remaining string?

__Solution method__

**Summary**

Yes : 8dm

Cut away: 3dm

The rest: … dm?

**The answer**

To find the remaining length of the rope, we subtract the length of the original rope from the length of the cut line.

__Solution guide__

The length of the remaining string in decimeters is:

8 – 3 = 5 (dm)

Answer: 5dm.

### 1.4. Solving Textbook Exercises page 10

Lesson 1

Calculate:

__Solution method__

Perform subtraction from right to left.

__Solution guide__

Lesson 2

Mental arithmetic:

60 – 10 – 30 = 90 – 10 – 20 = 80 – 30 – 20 =

60 – 40 = 90 – 30 = 80 – 50 =

__Solution method__

Perform the subtraction of tens digits and then add a 0 after the result you just found.

__Solution guide__

60 – 10 – 30 = 20 90 – 10 – 20 = 60 80 – 30 – 20 = 30

60 – 40 = 20 90 – 30 = 60 80 – 50 = 30

Set the calculation and then calculate the difference, knowing the number to be subtracted and subtracted is :

a) 84 and 31; b) 77 and 53; c) 59 and 19.

__Solution method__

– Set the calculation: Write the calculation in vertical rows, with numbers in the same row and columns together.

– Calculation: Perform subtraction of numbers in order from right to left.

__Solution guide__

From a piece of fabric 9dm long, cut out 5dm to sew a bag. How many decimeters is the remaining piece of cloth?

__Solution method__

**Summary**

Yes: 9dm

Cut out : 5dm

The rest: ….dm?

**The answer**

To find the length of the remaining fabric, subtract the length of the original piece of fabric from the length of the cut piece.

__Solution guide__

The remaining piece of fabric is decimeters long:

9 – 5 = 4 (dm)

Answer: 4dm.

Circle the word in front of the correct answer:

There are 84 chairs in the warehouse, 24 chairs have been taken out. How many chairs are left in stock?

A. 24 chairs B. 48 chairs C. 60 chairs D. 64 chairs.

__Solution method__

*Summary*

Yes: 84 chairs

Take out: 24 chairs

Left: … the chair?

**The answer**

To find the solution, we subtract the number of seats from the original number of seats.

__Solution guide__

In the remaining inventory the number of chairs is:

84 -24 = 60 (chair)

Answer: 60 chairs

**The answer to choose is C**

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