Objectives (5 - 10 minutes)

1. Understand the composition of numbers: Students should be able to understand the concept of composition, which is the joining of several parts to form a whole. They should learn to identify the parts (digits) that make up a number and how these parts relate to each other to form the number.

2. Understand the decomposition of numbers: Students should be able to understand the concept of decomposition, which is the separation of a whole into its constituent parts. They should learn to decompose a number into its units, tens and hundreds.

3. Practice the composition and decomposition of numbers: Students should be able to apply what they have learned about the composition and decomposition of numbers in a variety of practical activities. This includes performing simple addition and subtraction calculations using the regrouping (decomposition) and grouping (composition) strategy.

Secondary objectives:

• Stimulate critical thinking and problem solving: Through the proposed activities, students will be encouraged to analyze, reason and solve mathematical problems. This will help develop their critical thinking skills.

• Promote collaboration and communication: Students will be encouraged to work in teams, discuss their ideas and solutions, and express their thoughts in a clear and organized way. This will help promote their communication and collaboration skills.

Introduction (15 - 20 minutes)

1. Review of basic concepts: The teacher will begin the lesson by reminding students about the basic concepts of numbers and mathematical operations that were previously learned. This will include the idea that numbers are formed by digits (units, tens, hundreds) and that we can perform operations such as addition and subtraction with these numbers. (5 minutes)

2. Problem situations: Next, the teacher will present two problem situations to the students, which will be solved through the composition and decomposition of numbers.

   • Situation 1: The teacher will have a number of colored balloons and ask the students to help them separate them into groups by color. For example, if there are 153 balloons, the students will have to find out how many balloons are in each color group (units, tens, hundreds).

   • Situation 2: The teacher will have a box with an unknown number of candies and ask the students to guess how many candies are in the box. Then, the teacher will ask the students to use decomposition to explain how they arrived at this estimate. (10 minutes)

3. Contextualization: The teacher will explain to the students that the ability to compose and decompose numbers is very important in mathematics. For example, when we are solving an addition or subtraction problem, we need to decompose the numbers to make the calculation easier. In addition, in many everyday situations, we need to compose and decompose numbers, such as when we are counting money, reading a clock or following a kitchen recipe. (5 minutes)

4. Introduction to the topic: The teacher will then introduce the topic of the lesson: composition and decomposition of numbers less than 1000. He will explain that, just like in the balloon problem situation, numbers can be divided into parts (units, tens, hundreds) and that we can use this skill to make our calculations easier and solve problems. (5 minutes)

Development (20 - 25 minutes)

1. Flipped theory: The teacher will ask the students to watch short and interactive videos on the topic of the lesson before the class. These videos can be fun animations that explain the composition and decomposition of numbers in a simple and clear way. (5 - 10 minutes)

2. Activity 1 – "Building numbers": The teacher will give the students a set of cards with digits from 0 to 9. Each student will receive a three-digit number, such as 257. The challenge will be to "build" this number using the digit cards, placing them in the correct order. After the construction, the students will decompose the number, saying how many hundreds, tens and units the number has. (10 minutes)

3. Activity 2 – "Number puzzle": The teacher will have previously prepared simple number puzzles. Each puzzle will be a three-digit number (e.g. 486) divided into three parts (units, tens and hundreds). The parts will be mixed up and the students will have to put them together to form the correct number. This activity will reinforce the concept of number composition. (5 - 10 minutes)

4. Activity 3 – "Treasure hunt": The teacher can organize a mathematical "Treasure hunt" activity. Several objects will be hidden around the classroom, and each object will have a three-digit number (e.g. 623). The students, in groups, will receive clues to find the objects. When they find an object, they will have to decompose the number and write down the parts (hundreds, tens, units) on a piece of paper. In the end, the group with the most correctly decomposed numbers wins. (10 - 15 minutes)

The proposed activities are just suggestions, the teacher can choose one or more activities, depending on the time available and the pace of the class. The aim is that the activities are fun and challenging, encouraging students to apply the concepts learned in a fun and practical way. The teacher should be available to guide and assist students during the activities, clarifying doubts and stimulating reflection.

Feedback (10 - 15 minutes)

1. Group discussion: The teacher will gather all the students and ask them to share their solutions and findings from the group activities. Each group will have the opportunity to present the number they built (activity 1), the puzzle they solved (activity 2) or the numbers they found (activity 3) and how they performed the decomposition or composition. During the presentations, the teacher will ask questions to stimulate reflection and ensure that all students have understood the concepts of composition and decomposition of numbers. (5 - 7 minutes)

2. Connection with the theory: Next, the teacher will return to the theory of composition and decomposition of numbers, reinforcing the main concepts based on the activities carried out. He will highlight how the practical activities helped the students to better understand the theory and apply it in a meaningful way. The teacher can also present additional examples or ask questions to check the students' understanding. (3 - 5 minutes)

3. Final reflection: Finally, the teacher suggests a moment of individual reflection for the students. He will ask two simple questions and ask the students to think silently about them for a minute before sharing their answers.

   • Question 1: "How do you use or could you use the composition and decomposition of numbers in your life outside of school?"

   • Question 2: "What did you think of today's activities? How did they help you to better understand the composition and decomposition of numbers?"

   The teacher will give the students time to think about the questions and then invite some of them to share their answers with the class. This final reflection stage will allow students to consolidate their learning, make connections with everyday life and express their opinions on the activities carried out. (2 - 3 minutes)

Conclusion (5 - 10 minutes)

1. Lesson summary: The teacher will summarize the main points covered in the lesson, reinforcing the concept of composition and decomposition of numbers less than 1000. He will remind the students that composition is the joining together of several parts to form a whole, and decomposition is the separation of a whole into its constituent parts. The teacher will also highlight the importance of these concepts for mathematics and everyday life, explaining that the ability to compose and decompose numbers makes it easier to perform calculations and solve problems. (3 - 5 minutes)

2. Connection between theory and practice: Next, the teacher will explain how the lesson connected theory to practice. He will mention the fun activities that the students carried out, explaining that these activities were designed to help them understand and apply the theoretical concepts in a concrete and meaningful way. The teacher will also emphasize that the group discussion and individual reflection allowed students to consolidate their learning and make connections with everyday life. (2 - 3 minutes)

3. Extra materials: The teacher will suggest some extra materials for students who wish to deepen their knowledge on the subject. These materials may include interactive digital games that reinforce the concepts of composition and decomposition of numbers, educational websites with practical activities, and children's math books that approach the topic in a fun and accessible way. The teacher will emphasize that these materials are optional, but may be useful for students who wish to practice more and expand their understanding. (1 - 2 minutes)

4. Relevance of the subject: Finally, the teacher will briefly explain the importance of the subject for everyday life and for the students' continued learning. He will mention that the ability to compose and decompose numbers is fundamental for solving more complex mathematical problems, such as multiplication and division. In addition, the teacher will emphasize that mathematics is a discipline that is based on fundamental concepts, and that understanding these concepts from an early age can make it easier to learn more advanced topics in the future. (1 - 2 minutes)