Math 2 Lesson: 54 – 18

### 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 keyword “less than”; “remaining”… we often use subtraction to find the solution.

– Presentation of the problem.

– Check the solution and the results you just found.

### 1.3. Textbook exercise solution page 63

Lesson 1

Calculate:

__Solution method__

Perform subtraction of numbers in order from left to right.

__Solution guide__

**Lesson 2**

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

a) 74 and 47; b) 64 and 28; c) 44 and 19.

__Solution method__

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

– Calculation: Subtract numbers from right to left in turn.

__Solution guide__

**lesson 3**

The blue piece of cloth is 34dm long, the purple piece of cloth is 15dm shorter than the blue one. How many decimeters is the purple piece of cloth?

__Solution method__

To find how many decimeters of the purple piece of cloth, subtract 15dm from the length of the blue cloth.

__Solution guide__

The decimeter long piece of purple fabric is:

34 – 15 = 19 (dm)

Answer: 19dm.

### 1.4. Solving Textbook Exercises Page 64

**Lesson 1**

Mental arithmetic:

14 – 5 = 14 – 7 = 14 – 9 =

14 – 6 = 14 – 8 = 13 – 9 =

__Solution method__

Subtract the numbers and then fill in the blanks with the results.

__Solution guide__

14 – 5 = 9 14 – 7 = 7 14 – 9 = 5

14 – 6 = 8 14 – 8 = 6 13 – 9 = 4

**Lesson 2**

Calculate then calculate:

a) 84 – 47; 30 – 6; 74 – 49;

b) 62 – 28; 83 – 45; 60 – 12.

__Solution method__

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

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

__Solution guide__

**lesson 3**

Find x:

a) x – 24 = 34

b) x + 18 = 60

c) 25 + x = 84.

__Solution method__

– To find the number to be subtracted we take the difference of addition and subtraction.

– To find a term, we subtract the other term from the sum.

__Solution guide__

a) x – 24 = 34

x = 34 + 24

x = 58

b) x + 18 = 60

x = 60 – 18

x = 42

c) 25 + x = 84

x = 84 – 25

x = 59.

**Lesson 4**

A toy store has 84 cars and planes, including 45 cars. How many planes does that store have?

__Solution method__

To find out how many planes the store has, we subtract 84 from the number of cars given.

__Solution guide__

That store has a plane number:

84 – 45 = 39 (airplane)

Answer: 39 planes.

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