Grade 1
  1. Numbers and Counting  1.1. Counting to 10  1.2. Counting to 20  1.3. Counting to 50  1.4. Counting to 100  1.5. Writing Numbers 1 to 10  1.6. Writing Numbers 1 to 20  1.7. Writing Numbers 1 to 50  1.8. Writing Numbers 1 to 100  1.9. Reading Numbers 1 to 10  1.10. Reading Numbers 1 to 20  1.11. Reading Numbers 1 to 50  1.12. Reading Numbers 1 to 100  1.13. Comparing Numbers  1.14. Ordering Numbers  1.15. Odd and Even Numbers  1.16. Number Patterns  1.17. Skip Counting by 2s, 5s, and 10s  1.18. Understanding Zero
  2. Basic Addition and Subtraction  2.1. Understanding Addition  2.2. Addition Facts within 10  2.3. Addition Facts within 20  2.4. Adding Zero  2.5. Adding One More  2.6. Adding Two More  2.7. Adding Three More  2.8. Adding Using Pictures  2.9. Addition Word Problems  2.10. Understanding Subtraction  2.11. Subtraction Facts within 10  2.12. Subtraction Facts within 20  2.13. Subtracting Zero  2.14. Subtracting One  2.15. Subtracting Two  2.16. Subtraction Using Pictures  2.17. Subtraction Word Problems  2.18. Introduction to Doubles Facts  2.19. Introduction to Making 10
  3. Place Value and Number Sense  3.1. Understanding Tens and Ones  3.2. Counting by Tens  3.3. Place Value within 20  3.4. Place Value within 50  3.5. Place Value within 100  3.6. Reading and Writing Two-Digit Numbers  3.7. Comparing Two-Digit Numbers  3.8. Decomposing Numbers
  4. Measurement  4.1. Length  4.1.1. Comparing Lengths  4.1.2. Measuring with Non-Standard Units  4.1.3. Using Standard Units (Inches and Centimeters) in Length  4.2. Weight  4.2.1. Comparing Weights  4.2.2. Heavy and Light Objects  4.2.3. Introduction to Grams and Pounds  4.3. Capacity  4.3.1. Comparing Capacity  4.3.2. Full and Empty  4.3.3. Introduction to Liters and Milliliters  4.4. Time  4.4.1. Telling Time to the Hour  4.4.2. Telling Time to the Half Hour  4.4.3. Days of the Week  4.4.4. Months of the Year  4.4.5. Understanding Yesterday, Today, and Tomorrow  4.5. Money  4.5.1. Recognizing Coins  4.5.2. Counting Coins  4.5.3. Introduction to Dollar and Cents Symbols  4.5.4. Simple Addition and Subtraction with Money
  5. Geometry  5.1. 2D Shapes  5.1.1. Recognizing 2D Shapes  5.1.2. Drawing 2D Shapes  5.1.3. Naming 2D Shapes  5.1.4. Properties of 2D Shapes  5.1.5. Sorting 2D Shapes  5.1.6. Composing Simple Shapes  5.2. 3D Shapes  5.2.1. Recognizing 3D Shapes  5.2.2. Naming 3D Shapes  5.2.3. Properties of 3D Shapes  5.2.4. Sorting 3D Shapes  5.3. Position and Direction  5.3.1. Left and Right  5.3.2. Above and Below  5.3.3. Inside and Outside  5.3.4. Near and Far  5.3.5. In Front and Behind
  6. Patterns and Sorting  6.1. Recognizing Patterns  6.2. Extending Patterns  6.3. Creating Patterns  6.4. Sorting by Color  6.5. Sorting by Shape  6.6. Sorting by Size
  7. Data and Graphing  7.1. Introduction to Data  7.2. Collecting Data  7.3. Tally Marks  7.4. Bar Graphs  7.5. Picture Graphs  7.6. Interpreting Simple Graphs
  8. Fractions  8.1. Understanding Halves  8.2. Understanding Fourths  8.3. Dividing Shapes into Equal Parts  8.4. Identifying Equal and Unequal Parts

Grade 1 → Basic Addition and Subtraction ↓


Subtraction Facts within 20


Subtraction is one of the basic arithmetic operations that refers to taking away or removing. When we learn subtraction facts within 20, we are focusing on understanding how to subtract numbers that are less than or equal to 20. This is important for building a strong foundation in math.

Subtraction can be seen as the opposite of addition. While addition adds numbers together to make a larger number, subtraction subtracts something from the numbers to make a smaller number.

Basic concepts of subtraction

Subtraction helps to find out how much is left or how much is missing. It is represented by the minus sign -.

For example:

5 - 3 = 2

Here, 5 is the starting number, 3 is the number to be subtracted, and 2 is the result or difference.

Understanding subtraction

Let's use a simple visual example to understand subtraction better.

Start with 10 blocks remove 4 blocks 6 blocks left

In this example, we start with 10 blocks. We remove 4 blocks, and we are left with 6 blocks. This is represented as 10 - 4 = 6.

Subtraction facts within 20

Subtraction facts within 20 are simply subtraction problems you can do with the numbers 1 to 20. Becoming familiar with these helps students solve problems quickly and understand the relationship between numbers.

Examples of subtraction facts within 20

  • 16 - 5 = 11
  • 14 - 3 = 11
  • 20 - 4 = 16
  • 19 - 10 = 9
  • 18 - 18 = 0

Mastering these facts takes practice. Students should regularly engage in exercises that involve solving subtraction problems, recognizing patterns, and playing subtraction games.

Visualization of subtraction

Visualization can be a very powerful tool in understanding subtraction. When you can see the numbers, it helps to better understand the subtraction mechanics.

5 - 3 = ? 2 green circles left

In this example, there are initially 5 green circles, and then we remove 3 of them (represented by the red circles). We are left with 2 green circles, so 5 - 3 = 2.

Strategies for learning subtraction facts

Here are some effective strategies to help students master subtraction facts within 20:

1. Counting backwards

This strategy involves counting backwards to find the answer to a subtraction problem. For example, to solve 7 - 2, you could count the two numbers backwards from 7 (6, 5). So, 7 - 2 = 5.

2. Number lines

The number line is a great tool for demonstrating subtraction. Students can physically step back on the line according to the number they want to subtract.

1 2 3 4 5 6 7 8 9

If we're solving 8 - 3, start with 8 and go back 3 steps to get to 5. So, 8 - 3 = 5.

3. Using touch points

Tangent points are imaginary points on numbers that help students visualize subtraction. For example, the number 4 would have 4 tangent points, and as the numbers are subtracted, the tangent points appear to disappear.

4. Remembering the basic facts

By focusing on memorizing basic subtraction facts, students can become quicker at solving subtraction problems within 20. Games, flashcards, and songs can be effective in helping them memorize these facts.

5. Related to yoga

Because subtraction is the opposite of addition, students can use their knowledge of addition facts to solve subtraction problems. If a child knows that 5 + 3 = 8, they can manipulate the equation to understand 8 - 3 = 5.

Practicing subtraction facts within 20

Regular practice is the key to mastering any mathematical concept. Here are some practical examples and questions to practice subtraction facts within 20:

Example questions:

  • What is 12 - 7?
  • Solve 15 - 9.
  • If we subtract 4 from 18 then how much will be left?
  • We had 14 apples and we ate 6. How many are left now?
  • Subtract 10 from 20.

More exercises:

For extra practice, create a list of random subtraction problems for students to solve each day. Include a variety of examples such as:

  • 9 - 3 = 6
  • 17 - 8 = 9
  • 5 - 5 = 0
  • 12 - 11 = 1
  • 13 - 4 = 9

Encourage students to check their answers by adding the subtracted number to the result to see if it matches the original number.

Conclusion

Understanding and mastering subtraction facts within 20 is a crucial skill in early math education. It lays the groundwork for more advanced mathematical concepts. Through practice, visualization, and various strategies, students can master subtraction and gain confidence in their mathematical abilities.

As students become more comfortable with these facts, they will become more efficient problem-solvers in their daily tasks and will be prepared for more challenging math concepts in the future.


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Subtraction Facts within 20

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