# Perimeter of Squares, Rectangle, and Triangles Primary 3 Mathematics Third Term Lesson Notes Week 3

**Subject : Mathematics **

Topic : Perimeter of Regular Shapes

Term : Third Term

Week : Week 3

Objectives :

Content :

Good morning, class! Today, we are going to learn about the perimeter of shapes. Specifically, we’ll focus on squares, rectangles, and triangles. Are you ready? Let’s dive in!

1. Perimeter of a Square:

A square is a shape with four equal sides. To find the perimeter of a square, we simply need to add up the lengths of all its sides. Since all sides of a square are equal, we can use a simple formula: perimeter = 4 × side length.

For example, let’s say we have a square with a side length of 5 centimeters. To find the perimeter, we multiply the side length by 4: perimeter = 4 × 5 cm = 20 cm. So the perimeter of this square is 20 centimeters.

2. Perimeter of a Rectangle:

A rectangle is a shape with two pairs of opposite sides that are equal in length. To find the perimeter of a rectangle, we add up the lengths of all its sides. The formula for the perimeter of a rectangle is: perimeter = 2 × (length + width).

Let’s take an example. Imagine we have a rectangle with a length of 6 meters and a width of 4 meters. We can find the perimeter by plugging the values into the formula: perimeter = 2 × (6 m + 4 m) = 2 × 10 m = 20 meters. Therefore, the perimeter of this rectangle is 20 meters.

3. Perimeter of a Triangle:

A triangle is a shape with three sides. To find the perimeter of a triangle, we add up the lengths of all its sides. Unlike squares and rectangles, triangles don’t have a specific formula for the perimeter because the lengths of their sides can vary.

Let’s consider a triangle with side lengths of 3 kilometers, 4 kilometers, and 5 kilometers. To find the perimeter, we simply add up these lengths: perimeter = 3 km + 4 km + 5 km = 12 kilometers. So the perimeter of this triangle is 12 kilometers.

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Remember, class, the perimeter is the distance around the shape. By understanding the formulas and applying them to different shapes, you can find the perimeter easily. Practice with different examples to strengthen your understanding.

Now, it’s time for you to try some exercises on your own. I will give you a few shapes, and I want you to calculate their perimeters. Ready?

Exercise 1:

Square with a side length of 8 centimeters. What is the perimeter?

Exercise 2:

Rectangle with a length of 10 meters and a width of 3 meters. What is the perimeter?

Exercise 3:

Triangle with side lengths of 7 kilometers, 9 kilometers, and 12 kilometers. What is the perimeter?

Take your time, solve the exercises, and let me know your answers when you’re done.

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### Evaluation

1. The perimeter of a square with a side length of 6 units is _______.

a) 24 units

b) 30 units

c) 36 units

2. A rectangle has a length of 8 centimeters and a width of 5 centimeters. Its perimeter is _______.

a) 13 centimeters

b) 18 centimeters

c) 26 centimeters

3. The perimeter of a triangle with side lengths 6 meters, 8 meters, and 10 meters is _______.

a) 24 meters

b) 26 meters

c) 30 meters

4. A square has a perimeter of 24 centimeters. Its side length is _______.

a) 4 centimeters

b) 6 centimeters

c) 8 centimeters

5. The perimeter of a rectangle with a length of 12 units and a width of 7 units is _______.

a) 19 units

b) 26 units

c) 36 units

6. A triangle has a perimeter of 30 centimeters. If two sides measure 9 centimeters and 12 centimeters, the third side measures _______.

a) 5 centimeters

b) 9 centimeters

c) 18 centimeters

7. The perimeter of a square is 40 meters. Its side length is _______.

a) 8 meters

b) 10 meters

c) 16 meters

8. A rectangle has a perimeter of 42 centimeters. If its length is 12 centimeters, its width is _______.

a) 6 centimeters

b) 9 centimeters

c) 18 centimeters

9. The perimeter of a triangle with side lengths 5 units, 12 units, and 8 units is _______.

a) 20 units

b) 25 units

c) 30 units

10. A square has a perimeter of 48 centimeters. Its side length is _______.

a) 8 centimeters

b) 12 centimeters

c) 16 centimeters

Remember to choose the correct option for each question, and feel free to ask if you have any doubts!

Lesson Plan: Perimeter of Squares, Rectangles, and Triangles

Grade: Primary 3

Subject: Mathematics

Topic: Perimeter of Squares, Rectangles, and Triangles

Duration: 1 hour

Learning Objectives:

1. Understand the concept of perimeter and its significance in measuring the distance around shapes.

2. Identify and distinguish between squares, rectangles, and triangles.

3. Calculate the perimeter of squares, rectangles, and triangles using appropriate formulas.

4. Apply the knowledge of perimeter to solve real-life problems involving these shapes.

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Embedded Core Skills:

1. Numeracy skills: Addition, multiplication, and problem-solving.

2. Critical thinking: Analyzing shapes and finding patterns.

3. Measurement skills: Understanding units of measurement and applying them appropriately.

4. Logical reasoning: Making connections between different shapes and their corresponding perimeters.

Learning Materials:

1. Chart paper or whiteboard

2. Markers or chalk

3. Ruler or measuring tape

4. Square, rectangle, and triangle cutouts or diagrams

5. Worksheets or handouts for practice exercises

6. Calculator (optional)

7. Real-life objects or images representing squares, rectangles, and triangles

Presentation:

1. Begin the lesson by displaying a chart paper or drawing a table on the board. Divide it into three columns, labeling them as “Shape,” “Definition,” and “Properties.”

2. Discuss the meaning of perimeter and its importance in measuring the distance around shapes.

3. Introduce the three shapes: square, rectangle, and triangle. Provide their definitions and draw or display their respective diagrams or cutouts.

4. In the “Properties” column, discuss the unique characteristics of each shape, emphasizing the number of sides and their lengths.

5. Explain the formulas for calculating the perimeter of each shape:

– Square: perimeter = 4 × side length

– Rectangle: perimeter = 2 × (length + width)

– Triangle: Add the lengths of all three sides.

6. Clarify any doubts or questions before proceeding to the activities.

Teacher’s Activities:

1. Display or distribute the square, rectangle, and triangle cutouts or diagrams.

2. Model how to measure the sides of each shape using a ruler or measuring tape, and demonstrate how to calculate their perimeters.

3. Provide step-by-step explanations of the formulas for perimeter calculation, highlighting the importance of using the correct units of measurement.

4. Show examples of real-life objects or images that represent each shape, and discuss how to determine their perimeters.

Learners’ Activities:

1. Observe and actively participate in the teacher’s demonstrations and explanations.

2. Measure the sides of the given shapes using rulers or measuring tapes.

3. Calculate the perimeters of the shapes using the formulas provided.

4. Solve practice exercises individually or in small groups, applying the knowledge gained.

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Assessment:

1. Conduct ongoing formative assessment during the lesson by observing students’ engagement, participation, and understanding.

2. Provide immediate feedback and address any misconceptions or difficulties.

3. Administer a summative assessment at the end of the lesson using worksheets or handouts with ten evaluation questions.

Ten Evaluation Questions:

1. Calculate the perimeter of a square with a side length of 7 units.

2. Find the perimeter of a rectangle with a length of 9 centimeters and a width of 5 centimeters.

3. A triangle has side lengths of 6 meters, 8 meters, and 10 meters. What is its perimeter?

4. The perimeter of a square is 36 centimeters. What is its side length?

5. Determine the perimeter of a rectangle with a length of 12 units and a width of 6 units.

6. A triangle has a perimeter of 24 centimeters. If two sides measure 9 centimeters and 6 centimeters, what is the length of the third side?

7. The perimeter of a square is 48 meters. What is the length of each side?

8. Calculate the perimeter of a rectangle with a length of 15 centimeters and a width of 8 centimeters.

9. A triangle has side lengths of 5 centimeters, 7 centimeters, and 9 centimeters. Find its perimeter.

10. Determine the perimeter of a square with a side length of 10 meters.

Conclusion:

1. Recap the main points of the lesson, emphasizing the concept of perimeter and its application to squares, rectangles, and triangles.

2. Summarize the formulas for finding the perimeter of each shape and the importance of using appropriate units of measurement.

3. Encourage students to practice calculating perimeters in real-life scenarios and to look for these shapes around them.

4. Address any remaining questions or concerns.

5. Provide positive feedback on students’ efforts and progress.

Note: It is important to adapt the lesson plan to suit the specific needs, pace, and prior knowledge of the students. Additional activities, discussions, or modifications can be made as necessary to ensure effective learning.

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