Subtraction on a number line

Lesson Plan: Subtraction on a Number Line
Grade Level: 1
Topic: Subtracting Using a Number Line
 

Learning Objectives
By the end of the lesson, students should be able to:
Understand subtraction as “taking away”
Use a number line to subtract numbers up to 20
Move backward (left) on a number line to find answers
 

Materials Needed
marker/whiteboard 
   
Introduction 
Draw a number line (0–20).
Ask:
“What happens when we take something away?”
Explain:
Subtraction means taking away
On a number line, we move backward (to the left)
 

Teaching / Activity 
Step 1: Demonstration
Example: 5 − 2
Start at 5
Move 2 steps backward → 4, 3
Land on 3
 So, 5 − 2 = 3

2. 8 − 3
Start at 8
Move back 3 steps → 7, 6, 5
Answer: 5
 

3. 20 − 5
Start at 20, move 5 steps back → 15

4. 20 − 1
Start at 20, move 1 step back → 19

5. 20 − 7
Start at 20, move 7 steps back → 13

Step 3: Subtracting 3 Numbers 

When subtracting 3 numbers, we subtract the first 2 numbers then subtract the last number (third number) from the result of subtracting the first 2 numbers. See the number line above.

1. 8 − 3 − 2
Start at 8
Move back 3 → 5
Move back 2 → 3
Answer: 3
2. 14 − 2 − 2
Start at 14
Move back 2 → 12
Move back 2 → 10
Answer: 10
3. 12 − 5 − 1
Start at 12
Move back 5 → 7
Move back 1 → 6
Answer: 6

Guide them to count backward aloud.

Conclusion 
Review: Subtraction means taking away.
On a number line, we move backward.