## Key Concepts

- Number line.
- Count on to subtract.
- Count back to subtract.

## Introduction

**Example 1:**

The number line given below indicates all the numbers from 60 to 69.

Fill in the missing numbers in the number line.

**Solution:**

**Example 2:**

**Solution:**

### Count On to Subtract

**Example 3:**

Find 5 – 3.

**Solution**:

Step 1: Start with the lesser number.

Step 2: Count to 5 to find the **difference**.

Draw each move as you count.

3, 4, 5

It takes 2 moves to count from 3 to 5.

So, 5 – 3 = 2.

**Example 4:**

Find 11 – 4.

**Solution:**

Step 1: Start with the lesser number.

Step 2: Count to 11 to find the difference.

Draw each move as you count.

4, 5, 6, 7, 8, 9, 10, 11

It takes 7 moves to count on from 4 to 11.

So, 11 – 4 = 7.

### Count Back to Subtract

**Example 5:**

Find 5 – 3.

**Solution:**

Step 1: Start with the more significant number.

Step 2: Count back 3 moves to find the **difference**.

Count back 3 activities.

5, 4, 3, 2

You landed on 2.

So, 5 – 3 = 2.

**Example 6: **

Find 11 – 4.

**Solution**:

Step 1: Start with the more significant number.

Step 2: Count back 4 moves to find the difference.

Count back 4 activities.

11, 10, 9, 8, 7

You landed on 7.

So, 11 – 4 = 7.

## Exercise

1. Count on or count back to subtract. Show your work on the number line.

14 – 7 = ?

2. Count on or count back to subtract. Show your work on the number line.

14 – 8 = ?

3. Count on or count back to subtract. Show your work on the number line.

12 – 7 = ?

4. Count on or count back to subtract. Show your work on the number line.

9 – 7 = ?

5. Count on or count back to subtract. Show your work on the number line.

15 – 6 = ?

6. Count on or count back to subtract. Show your work on the number line.

15 – 9 = ?

7. Michael has 19 hens, and he gives 12 hens to his sister. How many hens does he have now?

8. 16 birds are sitting on a tree. 4 birds fly away. How many birds are on the tree now?

### What we have learned

- Understand the number line.
- Count on the number line to subtract.
- Count back the number line to subtract.

### Concept Summary

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