Math 2 Lesson: 51 – 15

### 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: Find x**

To find the unknown term, subtract the known term from the sum.

### 1.3. Textbook Exercises Page 50

**Lesson 1**

Calculate:

__Solution method__

Perform the subtraction in order from right to left.

__Solution guide__

**Lesson 2**

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

a) 81 and 44; b) 51 and 25; c) 91 and 9.

__Solution method__

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

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

__Solution guide__

**lesson 3**

Find x:

a) x+16=41

b) x+34=81

c) 19+x=61

__Solution method__

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

__Solution guide__

a) x+16=41

x=41−16

x=25

b) x+34=81

x=81−34

x=47

c) 19+x=61

x=61−19

x=42

### 1.4. Textbook Exercises Page 51

**Lesson 1**

Mental arithmetic:

11 – 2 = 11 – 4 = 11 – 6 = 11 – 8 =

11 – 3 = 11 – 5 = 11 – 7 = 11 – 9 =

__Solution method__

Perform subtraction 11 with a number and then fill in the blank with the result.

__Solution guide__

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

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

**Lesson 2**

Calculate then calculate:

a) 41 – 25; 51 – 35; 81 – 48

b) 71 – 9; 38 + 47; 29 + 6.

__Solution method__

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

– Calculation: Add or subtract numbers in order from right to left.

__Solution guide__

**lesson 3**

Find x:

a) x + 18 = 61

b) 23 + x = 71

c) x + 44 = 81

__Solution method__

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

__Solution guide__

a) x + 18 = 61

x = 61 − 18

x = 43

b) 23 + x = 71

x = 71 − 23

x = 48

c) x + 44 = 81

x = 81 − 44

x = 37

**Lesson 4**

A store with 51kg of apples sold 26kg of apples. How many kilograms of apples are left in that store?

__Solution method__

To find out how many kilograms of apples are left in the store, subtract the original weight from the volume of apples sold.

__Solution guide__

The store that has the kilos of apples left is:

51 – 26 = 25 (kg)

Answer: 25 kg of apples.

**Lesson 5**

Put “+” or “-” in the blank.

9 … 6 = 15 16 … 10 = 6 11 … 8 = 3

11 … 6 = 5 10 … 5 = 5 8 … 8 = 16

11 … 2 = 9 8 … 6 = 14 7 … 5 = 12

__Solution method__

– Compare the original number with the result:

+ If the initial number is greater than the result, you put a minus sign in the blank;

+ If the initial number is less than the result, put a plus sign in the blank.

__Solution guide__

9 + 6 = 15 16 – 10 = 6 11 – 8 = 3

11 – 6 = 5 10 – 5 = 5 8 + 8 = 16

11 – 2 = 9 8 + 6 = 14 7 + 5 = 12

.

=====

## Leave a Reply