Practice on solving Maths

### 1.1. Knowledge to remember

– How to solve and present more and less problems.

– How to find terms in a sum; subtracted number, minus number of a difference.

### 1.2. Math forms

**Form 1: More math problems**

To find a number with more values, I often use addition.

**Type 2: Less than problem**

**Form 3: Find the missing elements.**

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

– To find the number to be subtracted, we take the difference plus the minus number.

– To find the minus number, we subtract the difference from the subtracted number.

### 1.3. Textbook Exercises Page 88

**Lesson 1**

A shop sells 48 liters of oil in the morning and 37 liters in the afternoon. How many liters of oil did the store sell both times?

__Solution method__

To find out how many liters of oil sold in both sessions, we take the number of liters of oil sold in the morning plus the number of liters of oil sold in the afternoon.

__Solution guide__

In both sessions, the number of liters of oil sold is:

\(48 + 37 = 85\) (liters)

Answer: \(85\) liters of oil.

**Lesson 2**

Binh weighs 32kg, An weighs 6kg lighter than Binh. How many kilograms does An weigh?

__Solution method__

To find An’s weight, subtract 6kg from Binh’s weight.

__Solution guide__

An weight in kilograms is:

\(32 – 6 = 26\) (kg)

Answer: \(26\)kg.

**lesson 3**

Lan picked 24 flowers, Lien picked 16 flowers more than Lan. How many flowers did Lien pick?

__Solution method__

Want to find how many flowers Lien can pick, we take the number of flowers of Lan plus 16 flowers.

__Solution guide__

Lien picked the number of flowers:

\(24 + 16 = 40\) (flower)

Answer: \(40\) flower.

**Lesson 4**

Write the correct number in the blue boxes:

__Solution method__

Count up the numbers from 1 to 14 and then fill in the missing number in the blank.

__Solution guide__

### 1.4. Solve textbook exercises pages 88, 89

**Lesson 1**

Mental arithmetic:

12 – 4 = 9 + 5 = 11 – 5 = 20 – 8 =

15 – 7 = 7 + 7 = 4 + 9 = 20 – 5 =

13 – 5 = 6 + 8 = 16 – 7 = 20 – 4 =

__Solution method__

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

__Solution guide__

12 – 4 = 8 9 + 5 = 14 11 – 5 = 6 20 – 8 = 12

15 – 7 = 8 7 + 7 = 14 4 + 9 = 13 20 – 5 = 15

13 – 5 = 8 6 + 8 = 14 16 – 7 = 9 20 – 4 = 16

**Lesson 2**

Calculate then calculate:

28 + 19; 73 – 35; 53 + 47; 90 – 42.

__Solution method__

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

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

__Solution guide__

**lesson 3**

Find \(x\):

a) \(x + 18 = 62\)

b) \(x – 27 = 37\)

c) \(40 – x = 8\)

__Solution method__

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

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

– To find the minus number, we subtract the difference from the subtracted number.

__Solution guide__

a) \(x + 18 = 62\)

\(x = 62 – 18\)

\(x = 44\)

b) \(x – 27 = 37\)

\(x = 37 + 27\)

\(x= 64\)

c) \(40 – x = 8.\)

\(x = 40 – 8\)

\(x = 32\)

**Lesson 4**

The big pig weighs 92kg, the small pig is 16kg lighter than the big pig. How many kilograms does the baby pig weigh?

__Solution method__

To find how many kilograms the little pig weighs, we subtract 16kg from the mass of the big pig.

__Solution guide__

The baby pig’s weight in kilograms is:

92−16=76 (kg)

Answer: 76 kg.

**Lesson 5**

Use a ruler and pen to connect the points to get:

__Solution method__

– The right hand holds the pen, the left hand holds the ruler, put in two of the given points, connecting the slack into a straight line.

– Take turns drawing to be rectangle and quadrangle

__Solution guide__

### 1.5. Solve textbook exercises pages 89, 90

**Lesson 1**

Calculate:

__Solution method__

Perform addition or subtraction of numbers from right to left.

__Solution guide__

**Lesson 2**

Calculate:

14 – 8 + 9 = 15 – 6 + 3 = 9 + 9 – 15 =

5 + 7 – 6 = 8 + 8 – 9 = 13 – 5 + 6 =

16 – 9 + 8 = 11 – 7 + 8 = 6 + 6 – 9 =

__Solution method__

Take turns performing the calculations in order from left to right and then fill in the results in the blanks.

__Solution guide__

14 – 8 + 9 = 15 15 – 6 + 3 = 12 9 + 9 – 15 = 3

5 + 7 – 6 = 6 8 + 8 – 9 = 7 13 – 5 + 6 = 14

16 – 9 + 8 = 15 11 – 7 + 8 = 12 6 + 6 – 9 = 3

**lesson 3**

Write the correct number in the blank:

__Solution method__

a) To find the sum we take the two terms and add them together.

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

b) To find the difference, subtract the minus number from the subtracted number.

To find the number to be subtracted, we take the difference plus the minus number.

To find a minus number, we subtract the difference from the subtracted number.

__Solution guide__

**Lesson 4**

The small can can hold 14 liters of oil, the big can hold more than 8 liters of oil. How many liters of oil can the big can hold?

__Solution method__

To find how many liters of oil can the big can hold, we take the number of liters of the small can plus 8 liters.

__Solution guide__

The large can hold the number of liters of oil is:

14 + 8 = 22 (l)

Answer: 22 liters of oil.

**Lesson 5**

Draw a line 5cm long. Extend that line to get a straight line 1dm long.

__Solution method__

Use a ruler and pencil to draw a line 5cm long.

– Remember: 1dm = 10cm; From the line just drawn, stretch to get a straight line 10cm long.

__Solution guide__

### 1.6. Textbook Exercises Page 90

**Lesson 1**

Calculate then calculate:

a) 38 + 27; 54 + 19; 67 + 5

b) 61 – 28; 70 – 32; 83 – 8

__Solution method__

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

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

__Solution guide__

**Lesson 2**

Calculate:

12 + 8 + 6 = 25 + 15 – 30 =

36 + 19 – 19 = 51 – 19 + 18 =

__Solution method__

Perform calculations from left to right.

__Solution guide__

12 + 8 + 6 = 26 25 + 15 – 30 = 10

36 + 19 – 19 = 36 51 – 19 + 18 = 50

**lesson 3**

He is 70 years old this year, his father is 32 years younger than him. How old is the father this year?

__Solution method__

To find the age of our father, subtract 32 years from his age.

__Solution guide__

Father’s age this year is:

70 – 32 = 38 (age)

Answer: 38 years old.

**Lesson 4**

Write the correct number in the blank:

a) 75 + 18 = 18 + … b) 37 + 26 = … + 37

c) 44 + … = 36 + 44 d) … + 9 = 9 + 65

__Solution method__

Apply knowledge: a + b = b + a

__Solution guide__

a) 75 + 18 = 18 + 75 b) 37 + 26 = 26 + 37

c) 44 + 36 = 36 + 44 d) 65 + 9 = 9 + 65

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