Tổng hợp các dạng toán lớp 5 tỉ số phần trăm và hướng dẫn cách làm chi tiết

Percentages are a relatively difficult lesson in 5th grade math. Therefore, in this article Nguyễn Tất Thành will help you understand the theory and how to solve 5th grade math percentages. Teachers and parents can also refer to this article to guide children to learn more easily.

Theory of percentages in math grade 5

To solve 5th grade math percentage problems, you first need to understand the theory of percentages? What math operations are there for 5 billions? Nguyễn Tất Thành will explain these important knowledge clearly for you to understand immediately:

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Math percentages grade 5

A percentage is a ratio of two numbers in which we reduce the denominator of the ratio to 100. Percentage is often used to express the relative magnitude of one quantity compared to another.

• 1/100 can be written as 1%, or 1/100 = 1%;

• 15/100 can be written as 15%, or 15/100 = 15%;….

• In general, a/100 can be written as a%, or a/100 = a%

• The percent symbol is: %

To better understand the definition of 5th grade math percentage, we will learn more about 2 examples in the 5th grade math textbook pages 73, 74.

Grade 5 percentage calculations

Grade 5 math problems with percentages include 4 basic calculations: addition (+), subtraction (-), multiplication (x), division (:). Specifically:

• Addition: a% + b% = (a + b)%

• Subtraction: a% – b% = (a – b)%

• Multiplying a percentage by a number: a% xb = (axb)%

• Dividing a percentage by a number: a% : b = (a : b)%

Example: Calculate

a) 20% + 8%

b) 68% – 32%

c) 14% x 4

d) 48% : 4

Percentage math forms for grade 5

Through the theory section above, we have helped you understand what percentage is. In addition, students also need to understand the mathematical forms of percentages in grade 5 to be able to solve exercises in textbooks, workbooks or important exam questions.

Below is a summary of 5th grade math methods to solve math problems about percentages and instructions on how to solve them. You need to read carefully to understand the lesson.

Type 1: Problems about addition, subtraction, multiplication, and division of percentages

In the theory section of the 5th grade math textbook percentage above, Nguyễn Tất Thành has clearly stated the percentage calculations and specific examples. This is also the most common type of exercise that you need to pay attention to.

To solve math problems about percentages for grade 5 in the form of addition, subtraction, multiplication, and division of percentages, we need to do the same as for natural numbers, then write the percentage symbol (%) into it. On the right side is the calculated result.

Example: Calculate

a) 20% + 8%

b) 68% – 32%

c) 14% x 4

d) 48% : 4

Assignment

a) 20% + 8% = 28%

b) 68% – 32% =36%

c) 14% x 4 = 56%

d) 48% : 4 = 12%

Form 2: Find the percentage ratio of two numbers

To solve the 5th grade math exercise to find the percentage ratio of number A compared to number B, divide number A by number B and then multiply by 100.

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Formula: A : B x 100 = D%

In there:

• A is the number mentioned first.

• B is the number mentioned later.

• D is the percentage.

For example: Grade 4 of an elementary school has 200 students, including 80 male students.

a) Calculate the percentage ratio of the number of female students to the number of students in grade 4.

b) Calculate the percentage ratio of the number of male students to the number of students in grade 4.

Assignment

The number of female students in grade 4 is:

200 – 80 = 120 (students)

a) The percentage ratio of the number of female students to the number of students in grade 4 is:

120 : 200 x 100 = 60%

b) The percentage ratio of the number of male students to the number of students in grade 4 is:

80 : 200 x 100 = 40%

Answer: a) 60%; b) 40%

Form 3: Find the percentage value of a number

This grade 5 percentage math formula is as follows: To find the percentage value of a number, we divide that number by 100 and then multiply by the percentage, or multiply that number by the percentage and then divide by 100.

Example of math percentage calculation for grade 5:

Class 5A has 50 students, of which 60% are female students. How many female students are in the class?

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Assignment

The number of female students in class 5A is:

50 x 65 : 100 = 30 (students)

Answer: 26 students

Form 4: Find a number when you know the percentage value of that number

How to solve percentage math for grade 5 to find a number when knowing the percentage value of that number is as follows: Divide that value by the percentage and then multiply by 100 or take that value and multiply by 100 and then divide by the number of parts. hundred.

For example: A bottle of milk has 4.5% butter, know that the weight of butter in the bottle of milk is 18g. Calculate the amount of milk in a bottle.

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Assignment

The amount of milk in the bottle is:

18 : 4.5 x 100 = 400 (g)

Answer: 400g.

Type 5: Problems about calculating interest and capital

This type of 5th grade math problem about percentages is often applied in the field of trading. When encountering this type of exercise, students need to remember the 5th grade math formulas for calculating basic percentages below:

• Selling price = cost price + interest rate

• Cost price = selling price – interest rate

• Interest rate = selling price – cost price

• Selling price = cost price – loss

Example 1: A bicycle costs 2,000,000 VND, now discounted by 20%. What is the price of this bicycle now?

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Assignment

Consider the original price of the bicycle to be 100%, after discount:

100% – 20% = 80%

The current price of the bike is:

2000000 x 80 : 100 = 1600000 (VND)

Answer: 1600000 VND

Form 6: The problem is brought to a familiar mathematical form

For this type of 5th grade math percentage, we need to bring it back to a familiar exercise format to easily find the answer.

For example: The sum of two numbers is 25% and the quotient of those two numbers is also 25%. Find those two numbers.

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Assignment

25% = 0.25

The first number is: 0.25 : (1+4) = 0.05

The second number is: 0.25 – 0.05 = 0.2

Answer: 0.05 and 0.2

Some 5th grade math exercises with percentages for students to practice

After you have grasped the content of the 5th grade math lesson on percentages, you should regularly solve the exercises to consolidate your knowledge and test-taking skills. Below is a summary of math problems about percentages for grade 5 so you can practice on your own:

Lesson 1: If a product’s price has been reduced by 20%, if you want to sell that product at its original price, how much more percent must the price increase?

Lesson 2: After washing, a cloth shrinks by 2% of its original length. After washing, the fabric is only 24.5m long. How many meters long is the cloth before washing?

Lesson 3: The teacher divides the apples with the students. If each child has 9 balls, there are 9 balls missing. If we divide the match into 10 apples, we will lack 25% of the original number of apples. Calculate the number of apples she divided and the number of students who received apples.

Lesson 4: A construction contractor agreed to build a house at a cost of 360,000,000 VND, but the homeowner asked to reduce it by 2.5%, and the contractor agreed. Calculate the amount of money the contractor receives to build a house?

Lesson 5: Sea water contains 4% salt. How many grams of plain water should be added to 400 grams of sea water to make the salt ratio in the solution 2%?

Lesson 6: A person sells eggs: in the morning he sells 50% of the eggs, in the afternoon he sells the remaining 20%. Then that person sold 40 more fruits. At night, that person found that the number of eggs brought back was 120% of the number of eggs taken away. How many eggs did he bring?

Lesson 7: A class has 25% good students, 55% good students and the remaining average students. Calculate the number of students in that class if the average number of students is 5?

Lesson 8: Calculate the ages of two brothers knowing that 62.5% of my age is 75% older than my age by 2 years and 50% of my age is 37.5% older than my age by 7 years.

Lesson 9: The amount of salt contained in sea water is 5%. How many kg of plain water must be added to 200kg of seawater to get a solution containing 2% salt?

Lesson 10: The amount of water in fresh grass is 55%, in dry grass is 10%. How many kilograms of dry grass do we get from drying 100 kg of fresh grass?

Lesson 11: On March 26, a souvenir shop sells 10% off compared to normal days. However, they still profit 8% compared to the cost price. Ask what percentage of profit they make on a normal day compared to the cost price?

Lesson 12: In the school, 68% of students know Russian, 5% know both English and Russian. The rest only know English. What percentage of students in the school know English?

Lesson 13: A retailer bought a number of boxes of powdered milk for 24,000 VND/box. When paying, the seller gave the buyer an amount equal to 12.5% ​​of the price of a box. Then that person resells the above amount of milk with a profit equal to 33 1/3% of the cost price after a 20% reduction on the listed price. How much is the listed price on a box of milk?

Lesson 14: A fruit store orders 4.5 tons of oranges at a price of 18,000 VND per kilogram. Shipping cost is 1,600,000 VND. Suppose 10% of the oranges are damaged during shipping and all the oranges are sold. Calculate how much each kilogram of oranges needs to be sold to earn a profit of 8%?

Lesson 15: Dad bought 2 pairs of shoes for Tien, but they were both too small, so Mom had to sell them. Each pair of shoes sells for 300,000 VND. One pair sells 20% more than the purchase price, the other pair sells 20% less than the purchase price. Ask Tien’s mother how much profit or loss she made when she sold it?

Some notes to help children learn 5th grade math with good percentages

The 5th grade math problem about percentages is basically not easy but not difficult either. Therefore, if they do not study properly, it will be very difficult for them to answer the 5th grade math percentage exercises. Below are some tips to help you learn well in 5th grade math with percentages to keep in mind:

• Firmly grasp theoretical knowledge and how to calculate math percentages in grade 5: As with any lesson, remembering and understanding the lesson’s definition and calculation will help students easily recognize the lesson’s format. practice more. From there, you will also be able to solve exercises more easily.

• Practice diligently the advanced and basic 5th grade percentage math problems to hone your test-taking skills: Studying without practicing will not bring good results. Regularly practicing these types of exercises will help students remember knowledge more deeply and at the same time strengthen their test-taking skills.

• Combine learning with Nguyễn Tất Thành Math application to consolidate Math knowledge: This is a math teaching application for preschool and elementary school children according to the new GDPT program. The curriculum is methodically designed, with more than 60 topics, belonging to 7 major mathematical topics to help children master knowledge. Based on the age and learning level of each child, Nguyễn Tất Thành Math divides lessons into levels from easy to medium so that children can easily absorb them. Furthermore, this application also conveys knowledge in English, so it not only helps children develop mathematical thinking but also develop language very well. Therefore, parents should choose the Nguyễn Tất Thành Math application to help their children build a stronger foundation in mathematics and foreign languages.

Video introducing Nguyễn Tất Thành Math application.

Thus, through this article, Nguyễn Tất Thành has helped students master 5th grade math knowledge of percentages. In addition, parents should remind children to regularly follow the website monkey.edu.vn and study the Nguyễn Tất Thành Math application to learn more useful lessons.

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