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 → Place Value and Number Sense ↓


Place Value within 20


Introduction

Place value in math is a fundamental concept that helps us understand the value of each digit in a number. In first grade math, learning place value within 20 involves understanding how numbers are constructed using tens and ones. This understanding lays the groundwork for future math concepts involving larger numbers and mathematical operations.

Understanding place value

Place value indicates the value of a digit based on its place in a number. Each place in a number has a different value. For example, in the number 15, the digit '1' is in the 'tens' place and represents the value of ten, while the digit '5' is in the 'units' place and represents the value of five.

Points and their locations

In a two-digit number, each digit has a unique place value:

  • Units place: It is the rightmost digit. It represents the unit count.
  • Tens place: It is the digit just to the left of the units place. It shows how many tens there are in the number.

Let's look at some examples for better understanding:

Example 1: Understanding 12

The number 12 has two digits. The digit '1' is in the tens place, and the digit '2' is in the units place.

so:

1 Ten + 2 Ones = 12
1 ten 2 one

Example 2: Understanding 19

The number 19 has two digits. The digit '1' is in the tens place, and the digit '9' is in the units place.

so:

1 Ten + 9 Ones = 19
1 ten 9 Once

Manipulating numbers using place value

Understanding place value is essential when we manipulate numbers through addition and subtraction. It helps us break down numbers into manageable parts. For example, adding numbers within 20 can be easier when you separate the tens and ones.

Division of numbers

When you know the place value, you can divide numbers into tens and ones to simplify operations:

Example 3: Adding 13 and 4

Suppose we want to calculate:

13 + 4

First, divide 13 into tens and ones.

13 = 1 Ten + 3 Ones

Now add 4 to 3:

3 Ones + 4 Ones = 7 Ones

Put it all together:

1 Ten + 7 Ones = 17

Illustrating numbers through place value

Representing numbers by their place value helps children understand how numbers are composed.

Example 4: Visualizing the number 15

The number 15 can be viewed as a block of ten and five single units:

10 5 one

Summary

Place value is vital to understanding how numbers work, especially when working with numbers up to 20. Understanding the tens and ones in a number allows children to clearly see how numbers are made up, prepares them for addition and subtraction, and lays the groundwork for more complex math involving larger numbers. Breaking numbers apart and representing them as tens and ones can make math more understandable and less abstract.

Refining these basic skills will give children a better numerical understanding which will help them in maths in the years to come.


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Place Value within 20

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