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Subject: Mathematics
Semester: 2
Period: 5
Week: 27
School Name:
Teacher’s Name:
Subject: Mathematics
Grade Level: Grade 5
Date: Week 27
Lesson Duration: 45 minutes
Week & Period: Week 27, Period 5
Topic: Triangles and Quadrilaterals
Sub-topic: Classification of triangles and quadrilaterals
Learning Objectives
By the end of the lesson, students should be able to:
- Classify triangles by their sides and angles.
- Classify quadrilaterals by their properties.
- Draw and identify examples of triangles and quadrilaterals.
Previous Knowledge
Students already know how to measure and construct angles.
Instructional Materials
Mathematics textbook for Grade 5, rulers, protractors, cutout shapes
Lesson Development – ABC Model
A – Anticipation (Warm-up / Starter)
Time: 5–10 minutes
Teacher asks learners to recall the angles they studied in the previous lesson. Short activity: draw a triangle and identify its angles.
B – Building Knowledge (Main Lesson Body)
Time: 25–30 minutes
Classification of Triangles:
• By Sides:
o Equilateral Triangle: A triangle with three equal sides and three equal angles, each measuring 60°. It is symmetrical and all interior angles are equal.
o Isosceles Triangle: A triangle with two equal sides and two equal angles. The unequal side is called the base, and the equal angles lie opposite the equal sides.
o Scalene Triangle: A triangle with no equal sides and no equal angles. All sides and angles are of different lengths and degrees.
- By Angles:
o Acute-Angled Triangle: All three angles are less than 90°. It is the most common type of triangle.
o Right-Angled Triangle: Has one angle exactly 90°. The side opposite the right angle is called the hypotenuse, which is the longest side.
o Obtuse-Angled Triangle: Has one angle greater than 90° and the other two angles are acute (less than 90°).
Classification of Quadrilaterals:
• Square: A quadrilateral with four equal sides and four right angles (90° each). Opposite sides are parallel. All angles and sides are congruent.
• Rectangle: A quadrilateral with opposite sides equal and parallel and four right angles. Adjacent sides are not necessarily equal.
• Parallelogram: A quadrilateral with opposite sides equal and parallel, but angles are not necessarily 90°. Opposite angles are also equal.
• Rhombus: A quadrilateral with four equal sides, and opposite angles equal. It is like a slanted square. The diagonals bisect each other at right angles.
• Trapezoid (US)/Trapezium (UK): A quadrilateral with only one pair of parallel sides. The other pair is non-parallel. It can be symmetrical or asymmetrical.
Examples and Demonstrations:
• Teacher draws different types of triangles and quadrilaterals on the board, labeling their sides and angles.
• Examples:
- Draw a triangle with sides 6 cm, 6 cm, and 4 cm – classify as isosceles.
- Draw a triangle with angles 40°, 60°, and 80° – classify as acute-angled.
- Draw a quadrilateral with 4 equal sides and 90° angles – classify as a square.
- Identify a classroom whiteboard as a rectangle, and a diamond-shaped tile as a rhombus.
Learners’ Activities (Expanded):
• Learners classify cutout paper shapes provided by the teacher into the correct triangle or quadrilateral categories.
• Learners draw different triangles using rulers and protractors, then measure and label side lengths and angle measures to determine their type.
• In small groups, learners create a large poster or chart displaying types of triangles (by sides and by angles) and types of quadrilaterals, with diagrams and definitions for each.
• Each group presents their chart to the class, explaining each classification.
Assessment Checks:
• Oral Questions:
- “Which triangle has all sides equal?” (Equilateral)
- “Which triangle has one angle more than 90°?” (Obtuse-angled triangle)
- “What quadrilateral has one pair of parallel sides?” (Trapezoid)
- “Which quadrilateral has all sides equal but no right angles?” (Rhombus)
• Written Exercises: - Learners receive a worksheet with drawings of shapes and must classify each based on their properties.
- Identify and label triangle types from a given list of side lengths and angle measures.
- Match quadrilateral names with their correct properties in a matching exercise.
Notes (Expanded & Detailed):
Triangles are classified based on side lengths (equal or unequal) and angle sizes (less than, equal to, or more than 90°). Recognizing these differences helps learners apply geometric reasoning and solve problems in higher-level math and real-life contexts. Quadrilaterals are classified based on sides, angles, and parallelism. Some figures may share properties (e.g., a square is also a rectangle and a rhombus). Understanding these overlapping properties builds a deeper understanding of shape hierarchies and geometry relationships. This foundation prepares learners for more advanced geometry involving symmetry, transformations, and coordinate geometry.
C – Consolidation (Conclusion & Assessment)
Time: 5–10 minutes
Summary: Teacher reviews types of triangles and quadrilaterals with examples from learners.
Evaluation Method (Expanded):
Exit slip/quiz: Draw and label one equilateral triangle and one trapezoid. Teacher collects and gives oral feedback.
Assignment (Expanded):
Draw and classify 3 triangles and 3 quadrilaterals. Label sides and angles.
Follow-up Activity:
Learners cut out pictures of objects shaped like triangles or quadrilaterals from newspapers.
Differentiation / Inclusive Strategies
Provide stencils for learners who struggle with freehand drawing. Pair slower learners with advanced ones during classification.
Teacher’s Reflection (After Class)
What worked well? ___________________________________________
What needs improvement? ____________________________________
Students’ engagement level: ☑ High ☐ Medium ☐ Low