Class: Junior Secondary School 1 (JSS1, JSS 1)
Term: 2nd Term
Week: 2
Age: 12 years
Duration: 45 minutes
Subject: Mathematics
Curriculum Theme: Mathematics
Previous Lesson: Approximation and Rounding Off Numbers
Topic: Open Sentences
Subject Matter: Use of letters to represent numbers, Distinguish between open and closed sentences, Supplying the missing numbers in open sentences from a set of given permissible substitutes.

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:
(a) Identify open and closed sentences in mathematics.
(b) Use letters to represent unknown numbers in simple mathematical sentences.
(c) Supply missing numbers in open sentences from given permissible values.
Affective Domain:
(a) Develop interest and confidence in solving open sentences using symbols.
Psychomotor Domain:
(a) Practise solving mathematical open sentences on the board and in exercise books.
Social Domain:
(a) Work cooperatively in pairs or small groups to solve examples of open sentences.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum
Lagos State Unified Scheme of Work for Junior Secondary Schools
Math is Fun – Open Sentences
Relevant Textbooks

Instructional Materials

The teacher will teach this lesson with the aid of:

Chart showing examples of open and closed sentences
Flash cards with mathematical sentences
Whiteboard and markers
Number cards
Worksheet containing open sentences for practice

Rationale for the Lesson

This lesson helps students understand the relationship between numbers and symbols, and how to represent unknown values in mathematical sentences using letters.

Prerequisite/Previous Knowledge

Pupils have already learned about simple equations, basic arithmetic operations, and can perform addition, subtraction, multiplication, and division correctly.

Lesson Content/Board Summary

Open Sentences

An open sentence in mathematics is a statement that contains one or more variables (letters) whose values are not known. The truth or falsity of the sentence depends on the value of the variable.

Examples include:

( x + 5 = 8 )
( 2y – 3 = 7 )
( n times 4 = 12 )

Each of these sentences can be true or false depending on what number replaces the letter.

Closed Sentences

A closed sentence is a mathematical statement that is either true or false. It does not contain any unknown variable.

Examples are:

( 5 + 3 = 8 ) → True
( 6 – 4 = 1 ) → False
( 9 div 3 = 3 ) → True

These sentences have definite truth values because all numbers are known.

Using Letters to Represent Numbers

Letters such as ( x, y, a, b, n ) are used to represent unknown or changing numbers in mathematics. They are called variables.

Examples include:

If ( x + 3 = 7 ), then ( x = 7 – 3 = 4 ).
If ( 2y = 10 ), then ( y = 10 div 2 = 5 ).
If ( n – 6 = 9 ), then ( n = 9 + 6 = 15 ).

Supplying Missing Numbers in Open Sentences

To solve an open sentence means to find the number that makes the sentence true. This number is called the solution.

Examples include:

( x + 4 = 9 )
- To find ( x ), subtract 4 from both sides.
- ( x = 9 – 4 = 5 ).
( 3n = 12 )
- To find ( n ), divide both sides by 3.
- ( n = 12 div 3 = 4 ).
( p – 2 = 10 )
- To find ( p ), add 2 to both sides.
- ( p = 10 + 2 = 12 ).

The value that satisfies the sentence is the correct answer.

Teaching Methods/Instructional Techniques:

Discussion, Lecture, Explanation, Demonstration, Question and Answer, Group Work

Instructional Procedures

To deliver this lesson, the teacher will adopt the following steps:

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: Teacher writes “5 + 3 = 8” and “x + 3 = 8” on the board and asks pupils to describe the difference between them.
Pupils’ Activity: Pupils observe and respond that the second contains a letter instead of a number.
Learning Point: Pupils are introduced to the idea of using letters to represent unknown numbers.

Step 2: Explanation of Open and Closed Sentences

Time: 10 minutes
Teaching Skill: Explanation
Teacher’s Activity: Teacher defines and explains open and closed sentences using clear examples.
Pupils’ Activity: Pupils listen and take notes.
Learning Point: Pupils can distinguish between open and closed sentences.

Step 3: Use of Letters to Represent Numbers

Time: 10 minutes
Teaching Skill: Demonstration
Teacher’s Activity: Teacher solves examples on how letters can represent unknown numbers, showing each working on the board.
Pupils’ Activity: Pupils follow the steps and ask questions for clarity.
Learning Point: Pupils understand how to replace letters with correct numerical values.

Step 4: Solving Open Sentences

Time: 10 minutes
Teaching Skill: Practice and Application
Teacher’s Activity: Teacher presents open sentences and guides pupils to find the missing numbers using permissible values.
Pupils’ Activity: Pupils work out the examples individually and in groups.
Learning Point: Pupils can solve open sentences accurately.

Step 5: Note-Taking

Time: 5 minutes
Teaching Skill: Reinforcement
Teacher’s Activity: Teacher dictates or writes the board summary for pupils to copy.
Pupils’ Activity: Pupils copy the lesson notes neatly.
Learning Point: Pupils record key points from the lesson.

Step 6: Evaluation/Review

Time: 3 minutes
Teaching Skill: Questioning
Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

What is an open sentence?
What is a closed sentence?
Find the value of ( x ) in ( x + 7 = 12 ).
Solve ( 2y = 8 ).
Pupils’ Activity: Pupils answer the questions orally and on the board.
Learning Point: Pupils demonstrate understanding of the lesson objectives.

Step 7: Conclusion

Time: 2 minutes
Teaching Skill: Summarization
Teacher’s Activity: Teacher summarizes key points and encourages pupils to practise more open sentences at home.
Pupils’ Activity: Pupils listen and ask final questions.
Learning Point: Pupils understand the importance of symbols and open sentences in mathematics.

Home Task: Solve three new exercises on Open Sentences. Show each step and check each answer.

Lesson Keywords

Open Sentence – a statement with an unknown value represented by a letter.
Closed Sentence – a mathematical statement that is either true or false.
Variable – a letter representing an unknown number.
Equation – a mathematical statement showing equality between two expressions.
Solution – the value that makes an open sentence true.

Differentiation

Provide extra support for slower learners through guided examples, while advanced learners can create and solve their own open sentences.

Note for teachers using this lesson plan

Use simple numerical examples before introducing letters. Ensure pupils understand the logic behind each solution step. Encourage peer correction during group activities.