Types, Measurement and Sum of Angles Primary 5 Third Term Lesson Notes Mathematics Week 4
Subject : Mathematics
Term : Third Term
Class :Primary 5
Week : Week 4
Topic : Types, Measurement and Sum of Angles
Previous Lesson
Content
Good morning, class! Today, we will be diving into the wonderful world of angles. So, what exactly is an angle? Well, an angle is formed when two lines meet or intersect. It’s the space between those two lines, and we use angles to measure the amount of turn or rotation between them.
Now, let’s take a look at the different types of angles we have:
1. Acute Angle: An acute angle is an angle that measures less than 90 degrees. It’s like a tiny corner that’s smaller than a right angle. For example, if you have a slice of pizza and you fold it in half, the angle formed at the tip would be an acute angle.
2. Right Angle: A right angle is exactly 90 degrees. It forms a perfect Lshape, just like the corners of most books or the angle of a square. Picture a clock with its minute and hour hands pointing straight up at 12 o’clock, and you have a right angle.
3. Obtuse Angle: An obtuse angle is greater than 90 degrees but less than 180 degrees. It’s a wide angle that looks open, like the shape of a house rooftop. If you hold two pencils together in a Vshape with one end wider apart, you’ll have an obtuse angle.
4. Straight Angle: A straight angle is exactly 180 degrees. It forms a straight line, like a perfectly stretched out ruler. If you take a piece of paper and fold it in half from one corner to the other, the angle you get is a straight angle.
5. Reflex Angle: A reflex angle is greater than 180 degrees but less than 360 degrees. It’s like an angle that’s gone past the straight line and is bending back. Imagine a clock showing 7 o’clock, and you have a reflex angle.
These are the five main types of angles you’ll come across. Remember, angles are everywhere around us, from the corners of our rooms to the shape of a slice of cake. Now, it’s time for some practice. Take a look around the classroom and see if you can find examples of different types of angles. Raise your hand and share your findings with the class.
Topic: Meaning and Types of Angles
Class: Primary 5
 Introduction to Angles:
 Explain that an angle is a geometric figure formed by two rays or lines that originate from a common point called the vertex.
 Emphasize that angles are everywhere around us, in shapes, objects, and even in nature.
 Vertex and Arms:
 Define the vertex as the common endpoint where the two rays or lines meet.
 Define the arms as the two rays or lines that form the angle, extending from the vertex.
 Naming Angles:
 Explain that angles are named based on their vertex.
 Use examples to demonstrate naming angles, such as angle ABC or angle PQR.
 Types of Angles: a) Acute Angle:
 Define an acute angle as an angle that measures less than 90 degrees.
 Provide examples of acute angles, such as angles formed by a door opening or the corner of a book.
b) Right Angle:
 Define a right angle as an angle that measures exactly 90 degrees.
 Explain that a right angle can be identified by a small square at the vertex.
 Show examples of right angles, such as the corners of a table or a book.
c) Obtuse Angle:
 Define an obtuse angle as an angle that measures more than 90 degrees but less than 180 degrees.
 Give examples of obtuse angles, such as the angle between the hands of a clock at 3 o’clock.
d) Straight Angle:
 Define a straight angle as an angle that measures exactly 180 degrees.
 Explain that a straight angle appears as a straight line.
 Provide examples of straight angles, such as a line segment or the letter “L” lying flat.
e) Reflex Angle:
 Define a reflex angle as an angle that measures more than 180 degrees but less than 360 degrees.
 Use reallife examples to illustrate reflex angles, such as an angle formed by the hands of a clock at 9 o’clock.
 Angle Measurement:
 Explain that angles are measured in degrees using a protractor.
 Show the class how to use a protractor to measure angles accurately.
 Review and Practice:
 Summarize the different types of angles covered.
 Provide practice exercises for the students to identify and measure angles in various objects and shapes.
 Conclusion:
 Recap the main points covered in the lesson.
 Encourage students to observe angles in their surroundings and explore further on their own.
Remember, understanding angles is an important foundation for geometry and various mathematical concepts. Practice identifying and measuring angles to reinforce your knowledge.
Good morning, class! Today, we are going to learn about the meaning and types of angles.
An angle is formed when two rays share a common endpoint called the vertex. We use angles to measure the amount of turn between two lines or line segments. Now, let’s dive into the different types of angles:
 Acute angles:
 An acute angle is less than 90 degrees.
 Example 1: If you fold a piece of paper diagonally, the angle formed at the fold is acute.
 Example 2: Look at the corner of your notebook. The angle formed at the corner is acute.
 Right angles:
 A right angle measures exactly 90 degrees.
 Example 1: The corners of most books or tables form right angles.
 Example 2: When the minute and hour hands of a clock point to 12, they form a right angle.
 Obtuse angles:
 An obtuse angle is greater than 90 degrees but less than 180 degrees.
 Example 1: If you open your compass to draw a wide arc, the angle formed at the center is obtuse.
 Example 2: A kite has an obtuse angle where the two diagonals intersect.
 Straight angles:
 A straight angle is exactly 180 degrees. It forms a straight line.
 Example 1: When you extend your arms straight out to your sides, the angle between them is a straight angle.
 Example 2: The angle formed by the opposite sides of a square is a straight angle.
 Reflex angles:
 A reflex angle is greater than 180 degrees but less than 360 degrees.
 Example 1: If you make a complete turn while spinning around, the angle you’ve turned through is a reflex angle.
 Example 2: The angle formed by the minute hand of a clock when it points between two numbers is a reflex angle.
Now, let’s recap what we’ve learned today. We explored the meaning and types of angles, including acute angles, right angles, obtuse angles, straight angles, and reflex angles. Remember to observe your surroundings and look for reallife examples of these angles to deepen your understanding. Keep practicing, and you’ll become experts in no time!
Evaluation
 An angle is formed when ______________ meet. a) two lines b) two points c) two curves d) two shapes
 An angle that measures less than 90 degrees is called a(n) ______________ angle. a) acute b) obtuse c) right d) reflex
 A right angle measures ______________ degrees. a) 45 b) 90 c) 180 d) 360
 An obtuse angle is ______________ degrees. a) less than 90 b) exactly 90 c) greater than 90 d) exactly 180
 A straight angle measures ______________ degrees. a) less than 90 b) exactly 90 c) greater than 90 d) exactly 180
 A reflex angle is ______________ degrees. a) less than 90 b) exactly 90 c) greater than 90 d) greater than 180
 In a right angle, the two lines are ______________ to each other. a) parallel b) perpendicular c) intersecting d) curved
 The symbol used to represent an angle is ______________. a) % b) $ c) @ d) °
 An angle that is exactly 180 degrees is called a ______________ angle. a) right b) obtuse c) straight d) reflex
 The corners of most books form ______________ angles. a) acute b) obtuse c) right d) straight
Lesson 2
How To Measure Angles by using protractor
Good morning, grade 5 pupils! Today, we will learn how to measure angles using a very useful tool called a protractor. A protractor is a semicircular device with numbers and markings that allow us to measure angles accurately.
Let’s go through the steps together:
Step 1: Start by placing the protractor flat on the surface, ensuring that the center point (the midpoint of the straight edge) lines up with the vertex (the point where the two lines of the angle meet).
Step 2: Look at the bottom of the protractor. You will see a zerodegree mark (0°) in the center. This is where you align the protractor with one of the lines of the angle.
Step 3: Determine which direction you need to measure the angle. If the angle opens to the left, you will read the degrees counterclockwise. If it opens to the right, you will read the degrees clockwise.
Step 4: Now, look at the curved edge of the protractor. You will notice that it is marked with degree measurements. Read the number that aligns with the other line of the angle. This is the measure of your angle.
For example, let’s say we have an angle that opens to the right, and one of the lines aligns with the 0° mark on the protractor. If the other line aligns with the 45° mark on the curved edge, then the measure of the angle is 45 degrees.
Remember, when measuring angles, always ensure that the lines of the angle align with the appropriate marks on the protractor for an accurate measurement.
Now, it’s time for some practice! Each of you will receive a protractor and a worksheet with different angles. Use your protractor to measure the angles and write down their measurements. Raise your hand if you need any help, and I will be there to assist you.
Remember, practice makes perfect when it comes to measuring angles with a protractor. So, let’s get started and have fun with our angle measurements!
 A protractor is a ______________ shaped measuring tool used to measure angles. a) circular b) triangular c) rectangular d) semicircular
 The center point of the protractor is called the ______________. a) vertex b) midpoint c) base d) degree
 To measure an angle, place the protractor’s center point on the ______________ of the angle. a) right side b) left side c) vertex d) midpoint
 When measuring an angle that opens to the left, you read the degrees ______________. a) clockwise b) counterclockwise c) upward d) downward
 The zerodegree mark on the protractor is aligned with ______________. a) one line of the angle b) both lines of the angle c) the midpoint of the protractor d) the curved edge of the protractor
 If the measure of one line of the angle aligns with the 30° mark on the curved edge, the angle measures ______________ degrees. a) 30 b) 45 c) 60 d) 90
 Measuring an angle clockwise means reading the degrees from ______________. a) left to right b) right to left c) bottom to top d) top to bottom
 When measuring an angle, always ensure that the lines of the angle align with the appropriate marks on the ______________. a) ruler b) compass c) calculator d) protractor
 The measure of an angle is written in ______________. a) millimeters b) centimeters c) degrees d) inches
 The measure of a straight angle is always ______________ degrees. a) 45 b) 90 c) 180 d) 360
How To use parallel and transversal lines to determine corresponding, alternate, and vertically opposite angles
Good day, grade 5 pupils! Today, we will explore the relationship between parallel and transversal lines and how they help us determine corresponding, alternate, and vertically opposite angles. Understanding these angle relationships can be quite exciting, so let’s dive in!
First, let’s define some important terms:
1. Parallel Lines: Parallel lines are lines that never intersect. They remain the same distance apart from each other at all points. Imagine a pair of train tracks running side by side, and you’ll get the idea of parallel lines.
2. Transversal Line: A transversal line is a line that intersects two or more other lines. It cuts across the parallel lines, creating various angles where they meet.
Now, let’s explore the different types of angles that are formed:
1. Corresponding Angles: Corresponding angles are located on the same side of the transversal and in the same relative position in relation to the parallel lines. They are equal in measure. Look at the diagram below:
In the diagram, angles m and the angles on the same side of the transversal that are in the same position in relation to the parallel lines are called corresponding angles.
2. Alternate Angles: Alternate angles are located on opposite sides of the transversal and in the same relative position in relation to the parallel lines. They are equal in measure. Look at the diagram below:
In the diagram, angles n and the angles on the opposite side of the transversal that are in the same position in relation to the parallel lines are called alternate angles.
3. Vertically Opposite Angles: Vertically opposite angles are formed when two lines intersect. They are opposite each other, and their measures are equal. Look at the diagram below:
In the diagram, angle 1 and angle 2 are vertically opposite angles.
These angle relationships are useful for solving various geometric problems and proving theorems. So, keep an eye out for parallel lines and transversals in your math problems.
Now, it’s time for some practice! I will give you a worksheet with several pairs of parallel lines intersected by a transversal. Identify the corresponding angles, alternate angles, and vertically opposite angles in each case. Use your knowledge of these angle relationships to solve the problems. Raise your hand if you need any assistance, and I’ll be there to help you.
Remember, practice makes perfect when it comes to identifying these angle relationships. So, let’s have fun exploring the world of parallel lines and transversals and discovering the amazing angles they create!
Evaluation
1. Corresponding angles are located on the ______________ side of the transversal and in the same relative position in relation to the parallel lines.
a) same
b) opposite
c) left
d) right
2. Corresponding angles are ______________ in measure.
a) unequal
b) complementary
c) equal
d) supplementary
3. Alternate angles are located on ______________ sides of the transversal and in the same relative position in relation to the parallel lines.
a) same
b) opposite
c) left
d) right
4. Alternate angles are ______________ in measure.
a) unequal
b) complementary
c) equal
d) supplementary
5. Vertically opposite angles are ______________ each other.
a) adjacent to
b) parallel to
c) opposite to
d) perpendicular to
6. Vertically opposite angles have ______________ measures.
a) different
b) complementary
c) equal
d) supplementary
7. If two lines are parallel, the corresponding angles are always ______________.
a) equal
b) unequal
c) complementary
d) supplementary
8. If two lines are parallel, the alternate angles are always ______________.
a) equal
b) unequal
c) complementary
d) supplementary
9. If two lines are parallel, the vertically opposite angles are always ______________.
a) equal
b) unequal
c) complementary
d) supplementary
10. A transversal line intersects ______________ parallel lines.
a) one
b) two
c) three
d) four
Good day, grade 5 pupils! Today, we will explore the concept of the sum of angles on a straight line. It’s a fascinating topic, so let’s dive right in!
Imagine you have a straight line, like a ruler or a line segment. Let’s call it line AB. When we place an angle on this straight line, the two rays of the angle will always form a straight line with the line AB.
Now, here’s an interesting fact: The sum of the two angles formed on a straight line is always 180 degrees. In other words, if we add up the measures of the two angles, the total will always be 180 degrees.
To understand this concept better, let’s look at some examples:
Example 1:
In the diagram below, line AB is a straight line. Angle 1 measures 60 degrees. What is the measure of angle 2?
A_______1_______B




2
Solution:
Since angles 1 and 2 are formed on a straight line, their sum must be 180 degrees. We know angle 1 measures 60 degrees. Therefore, to find the measure of angle 2, we subtract the measure of angle 1 from 180:
180 – 60 = 120 degrees
Hence, the measure of angle 2 is 120 degrees.
Example 2:
In the diagram below, line CD is a straight line. Angle 3 measures 110 degrees. What is the measure of angle 4?
C_______3_______D




4
Solution:
Since angles 3 and 4 are formed on a straight line, their sum must be 180 degrees. We know angle 3 measures 110 degrees. Therefore, to find the measure of angle 4, we subtract the measure of angle 3 from 180:
180 – 110 = 70 degrees
Hence, the measure of angle 4 is 70 degrees.
Remember, this rule holds true for any pair of angles formed on a straight line. The sum of their measures will always be 180 degrees.
Now, it’s time for some practice! I will provide you with worksheets containing different diagrams with angles on straight lines. Find the missing angle by subtracting the known angle from 180 degrees. Raise your hand if you need any help, and I’ll be there to assist you.
Keep practicing, and soon you’ll become experts at finding the sum of angles on a straight line!
Evaluation
1. The sum of angles on a straight line is always ______________ degrees.
a) 90
b) 120
c) 180
d) 360
2. If one angle on a straight line measures 80 degrees, the other angle measures ______________ degrees.
a) 80
b) 100
c) 120
d) 180
3. If the measure of angle A on a straight line is 110 degrees, the measure of angle B is ______________ degrees.
a) 110
b) 130
c) 150
d) 180
4. If the measure of angle X on a straight line is 45 degrees, the measure of angle Y is ______________ degrees.
a) 45
b) 90
c) 135
d) 180
5. If the measure of angle P on a straight line is 30 degrees, the measure of angle Q is ______________ degrees.
a) 30
b) 60
c) 90
d) 180
6. The sum of angles on a straight line can be represented by the equation ______________.
a) A + B = 90
b) A + B = 120
c) A + B = 180
d) A + B = 360
7. If angle M on a straight line measures 120 degrees, the measure of angle N is ______________ degrees.
a) 120
b) 150
c) 180
d) 240
8. If angle R on a straight line measures 75 degrees, the measure of angle S is ______________ degrees.
a) 75
b) 105
c) 135
d) 180
9. The sum of two angles on a straight line is 140 degrees. If one angle measures 60 degrees, the other angle measures ______________ degrees.
a) 60
b) 80
c) 100
d) 120
10. If the measure of angle K on a straight line is 160 degrees, the measure of angle L is ______________ degrees.
a) 160
b) 180
c) 200
d) 360
Take your time, carefully choose the correct options for each question, and once you’ve made your choices, we can go through the answers together.
Lesson Plan Presentation: Meaning and Types of Angles & How to Measure Angles using a Protractor
Grade: Primary 5
Subject: Mathematics
I. Learning Objectives:
By the end of this lesson, students will be able to:
1. Define an angle as a space between two lines that meet.
2. Identify and describe the different types of angles (acute, right, obtuse, straight, and reflex).
3. Understand the concept of measuring angles using a protractor.
4. Measure angles accurately using a protractor.
5. Apply knowledge of angle measurement to solve problems and identify angle relationships.
II. Embedded Core Skills:
1. Critical thinking: Students will analyze and classify different types of angles.
2. Measurement skills: Students will learn to measure angles accurately using a protractor.
3. Problemsolving: Students will apply their knowledge of angle measurement to solve problems and identify angle relationships.
4. Communication: Students will engage in class discussions and share their findings.
III. Learning Materials:
1. Whiteboard, markers, and chart paper.
2. Protractors for each student.
3. Angle worksheets and practice problems.
4. Examples of different angle types (pictures or diagrams).
5. Reallife objects demonstrating angles (e.g., books, pizza slices, clock hands).
IV. Presentation:
a. Introduction (5 minutes):
– Greet the students and provide a brief overview of the lesson.
– Introduce the topic of angles by explaining that angles are formed when two lines meet.
– Emphasize that angles are everywhere around us and play a crucial role in understanding shapes and measurements.
b. Meaning and Types of Angles (10 minutes):
– Define an angle as a space between two lines that meet.
– Present examples of angles in reallife contexts, such as the corners of books, the shape of a slice of pizza, or clock hands.
– Introduce and explain the different types of angles: acute, right, obtuse, straight, and reflex.
– Use visual aids and diagrams to illustrate each type of angle, highlighting their characteristics and examples.
c. How to Measure Angles using a Protractor (15 minutes):
– Introduce the protractor as a tool for measuring angles accurately.
– Explain the different parts of a protractor: the center point, the straight edge, and the curved edge with degree markings.
– Demonstrate stepbystep how to measure an angle using a protractor, emphasizing the correct alignment with the lines and reading the degree markings.
– Provide examples and practice problems for students to try measuring angles on their own, guiding them through the process.
V. Teacher’s Activities:
1. Present the lesson content clearly and effectively, using visuals and reallife examples to enhance understanding.
2. Demonstrate the steps for measuring angles using a protractor.
3. Encourage student participation by asking questions, promoting class discussions, and addressing any misconceptions.
4. Provide guidance and support to students during individual and group activities.
5. Monitor student progress and provide timely feedback.
VI. Learners’ Activities:
1. Actively listen and engage in class discussions.
2. Observe and analyze visual examples of different types of angles.
3. Participate in handson activities, such as measuring angles using protractors.
4. Work individually or in groups to solve practice problems and identify angle relationships.
5. Ask questions and seek clarification when needed.
VII. Assessment:
1. Formative Assessment: Monitor student participation and understanding during class discussions and activities.
2. Summative Assessment: Evaluate students’ comprehension and application of angle measurement through practice problems and worksheets.
VIII. Evaluation Questions:
1. What is the definition of an angle?
2. Name three types of
Certainly! Here are the remaining evaluation questions:
8. Name three types of angles that are greater than 90 degrees.
9. What is the measure of a straight angle?
10. Explain the steps involved in measuring an angle using a protractor.
11. If two lines are parallel, what can you say about their corresponding angles?
12. In a triangle, if one angle measures 40 degrees and another angle measures 60 degrees, what is the measure of the third angle?
13. True or False: The sum of angles on a straight line is always 360 degrees.
14. Identify the type of angle: 30 degrees.
15. True or False: A reflex angle measures less than 180 degrees.
16. If angle A measures 75 degrees and angle B measures 105 degrees, what is the sum of their measures?
17. How are alternate angles different from corresponding angles?
18. Draw an acute angle and label its vertex and rays.
IX. Conclusion (5 minutes):
– Summarize the main points covered in the lesson, including the meaning and types of angles and how to measure angles using a protractor.
– Emphasize the importance of angles in understanding shapes, geometry, and measurements.
– Encourage students to practice their angle measurement skills in reallife scenarios and continue exploring the world of angles.
X. Homework:
– Assign anglerelated problems from the textbook or worksheet to reinforce understanding and practice measuring angles using a protractor.
– Encourage students to observe and identify angles in their surroundings and make a list of different types of angles they encounter.
Note: The duration of each section and the overall lesson plan may vary based on the specific needs and pace of the class. Flexibility is encouraged to ensure students’ engagement and understanding throughout the lesson.