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Subject: Mathematics
Semester: 1
Period: 3
Week: 14
School Name:
Teacher’s Name:
Subject: Mathematics
Grade Level: Grade 3
Date: Week 14
Lesson Duration: 45 minutes
Week & Period: Week 14, Period 3
Topic: Solving Open Sentence Problems with One Variable
Sub-topic: Simple Algebraic Expressions
Learning Objectives
By the end of the lesson, students should be able to:
Identify unknowns in number sentences
Solve simple open sentences with one variable using inverse operations
Apply algebra in solving word problems
Previous Knowledge
Students already know how to solve basic addition, subtraction, multiplication, and division problems.
Instructional Materials
Mathematics textbook, flashcards with missing number problems, counters, whiteboard
Lesson Development – ABC Model
A – Anticipation (Warm-up / Starter)
Time: 5–10 minutes
Teacher writes 5 + __ = 9 and asks: What number makes this true? Teacher encourages learners to shout the missing number. Teacher introduces the concept of an unknown.
B – Building Knowledge (Main Lesson Body)
Time: 25–30 minutes
Teacher defines open sentences as mathematical statements with a missing number or variable. Examples: x + 5 = 9, n × 4 = 24.
Teacher demonstrates solving using inverse operations: If x + 5 = 9, then x = 9 – 5 = 4.
Examples:
x – 3 = 10 → x = 10 + 3 = 13
4x = 20 → x = 20 ÷ 4 = 5
x ÷ 2 = 6 → x = 6 × 2 = 12
Learners’ Activities (Expanded):
Students work in pairs to solve missing number flashcards.
Students complete matching card games (equations with solutions).
Students create their own open sentences for peers to solve.
Assessment Checks:
Solve for x: x + 7 = 15, 3x = 18, x – 6 = 11.
Notes (Expanded & Detailed):
An unknown is a number we do not know yet, represented by symbols like x or n. We solve open sentences by using inverse operations to isolate the unknown. Algebra helps us model and solve everyday problems with missing values.
C – Consolidation (Conclusion & Assessment)
Time: 5–10 minutes
Summary: Teacher reviews solving open sentences with one variable using addition, subtraction, multiplication, and division.
Evaluation Method (Expanded):
Exit slip/quiz: Solve for x: x + 4 = 10, 5x = 25, x – 8 = 7.
Teacher collects and reviews answers.
Assignment (Expanded):
Complete 10 problems from the textbook on solving for unknowns.
Follow-up Activity:
Students write and solve their own open sentences with one variable at home.
Differentiation / Inclusive Strategies
Provide visual aids and concrete examples for weaker learners. Encourage peer tutoring for struggling students.
Teacher’s Reflection (After Class)
What worked well? ___________________________________________
What needs improvement? ____________________________________
Students’ engagement level: ☑ High ☑ Medium ☑ Low