Using a Number Line for Addition and Subtraction | Year 2 Mathematics (Cambridge) PDF Download

Introduction

Hello children! Today we will learn how to use a number line to help us with addition and subtraction. Make sure you have a piece of paper and a pencil ready so you can work along with me.

Addition Using a Number Line

Words That Mean Add

Before we start, let’s remember some words that mean the same as "add":

• Plus
• Sum
• Total
• Together
• More

These words tell us to add two or more numbers together.

Example: Adding Single-Digit Numbers

Let's use a number line to add 9 and 7:

• Find 9 on the number line.
• Count 7 steps forward.

So, 9 + 7 = 16.

Example: Adding Two-Digit Numbers

When adding larger numbers, you might need to draw your own number line.

Example: Add 25 and 9.

• Write 25 on the left side of the number line.
• Count 9 steps forward.

25 + 9 = 34.

Using Partitioning for Larger Numbers

Sometimes we add two larger numbers. We can break (partition) the second number into tens and ones to make it easier.
Example: Add 54 and 12.

• Break 12 into 10 and 2.
• Add 54 and 10 (54 + 10 = 64).
• Then add 2 (64 + 2 = 66).

So, 54 + 12 = 66.

Subtraction Using a Number Line

Words That Mean Subtract

Let's remember some words that mean the same as "subtract":

• Take away
• Difference
• Less
• Fewer
• Minus

These words tell us to subtract one number from another.

Example: Subtracting Single-Digit Numbers

Let's use a number line to subtract 6 from 14:

• Find 14 on the number line.
• Count 6 steps backward.

Example: Subtracting Two-Digit Numbers

Sometimes we need to draw our own number line to subtract.
Example: Subtract 7 from 28.

• Write 28 on the right side of the number line.
• Count 7 steps backward.

28 - 7 = 21.

Crossing the Tens Fence

Sometimes subtracting means crossing from one group of tens to another.
Example: Subtract 9 from 37.

• Break 9 into 7 and 2.
• Subtract 7 first (37 - 7 = 30).
• Then subtract 2 (30 - 2 = 28).

So, 37 - 9 = 28.

Summary

We learned how to use a number line for addition and subtraction:

• Addition involves counting steps forward.
• Subtraction involves counting steps backward.
• Partitioning helps with larger numbers.
• Crossing the tens fence is when you subtract across tens.