Grade 2
  1. Number Sense and Operations  1.1. Counting and Number Sequences  1.1.1. Counting up to 100  1.1.2. Counting by 2s, 5s, and 10s  1.1.3. Counting Backward from 20  1.1.4. Odd and even numbers in counting sequences  1.2. Place Value  1.2.1. Understanding ones and tens  1.2.2. Comparing Two-Digit Numbers  1.2.3. Identifying the Value of Each Digit in a Number  1.2.4. Building numbers using tens and ones  1.3. Addition and Subtraction  1.3.1. Basic addition up to 20  1.3.2. Basic subtraction up to 20  1.3.3. Addition with Regrouping  1.3.4. Subtraction with Borrowing  1.3.5. Solving word problems involving addition and subtraction  1.3.6. Addition and Subtraction with Multiples of 10  1.4. Odd and Even Numbers  1.4.1. Identifying Odd and Even Numbers  1.4.2. Understanding patterns in odd and even numbers  1.4.3. Simple operations with odd and even numbers
  2. Fractions and Decimals  2.1. Introduction to Fractions  2.1.1. Understanding halves and quarters  2.1.2. Representing fractions visually  2.1.3. Simple Fraction Comparisons  2.1.4. Writing Simple Fractions  2.1.5. Fractions as part of a whole  2.2. Fraction Equivalency  2.2.1. Understanding Equal Parts  2.2.2. Identifying Equivalent Fractions
  3. Measurement and Data  3.1. Length Measurement  3.1.1. Measuring objects using rulers  3.1.2. Comparing lengths  3.1.3. Estimating lengths  3.1.4. Understanding units of measurement (centimeters and inches)  3.1.5. Relating Length Measurements to Real-World Objects  3.2. Weight and Mass Measurement  3.2.1. Comparing Weights of Objects  3.2.2. Estimating weight in grams and kilograms  3.2.3. Using balance scales for comparison  3.3. Volume and Capacity Measurement  3.3.1. Understanding capacity with cups and liters  3.3.2. Comparing capacities of containers  3.3.3. Introduction to Milliliters  3.4. Time  3.4.1. Reading analog and digital clocks  3.4.2. Understanding hours and minutes  3.4.3. Calculating elapsed time in hours  3.4.4. Days of the week and months of the year  3.4.5. Understanding AM and PM  3.5. Money  3.5.1. Recognizing coins and bills  3.5.2. Counting money up to $1  3.5.3. Simple Addition and Subtraction with Money  3.5.4. Making Change for a Dollar
  4. Geometry and Spatial Reasoning  4.1. Shapes and Their Attributes  4.1.1. Identifying basic shapes (circle, triangle, square, rectangle)  4.1.2. Understanding sides and corners  4.1.3. Distinguishing between 2D and 3D shapes  4.1.4. Recognizing 3D Shapes (Cube, Sphere, Cone, Cylinder)  4.1.5. Composing and Decomposing Shapes  4.2. Symmetry  4.2.1. Understanding Lines of Symmetry  4.2.2. Drawing Symmetrical Shapes  4.2.3. Identifying Symmetrical Objects in the Environment  4.3. Patterns and Spatial Awareness  4.3.1. Recognizing and Creating Patterns  4.3.2. Extending Patterns  4.3.3. Understanding positions (left, right, above, below)  4.3.4. Using a grid to locate objects
  5. Data Handling and Probability  5.1. Collecting and Organizing Data  5.1.1. Using tally marks  5.1.2. Reading Bar Graphs  5.1.3. Simple Pictographs  5.1.4. Creating Bar Graphs from Given Data  5.2. Interpreting Data  5.2.1. Answering questions based on data  5.2.3. Identifying Most and Least in Data Sets  5.3. Introduction to Probability  5.3.1. Understanding likely and unlikely events

Grade 2 → Number Sense and Operations → Addition and Subtraction ↓


Addition and Subtraction with Multiples of 10


Understanding addition and subtraction with multiples of 10 is an important skill in early math. It helps develop a child's number sense and lays the groundwork for future mathematical concepts. In this lesson, we will explore what adding and subtracting using multiples of 10 is and how it can be done in a simple way. Throughout this lesson, we will use simple language and lots of explanations to make it easy to understand. We will also use visual examples to help demonstrate how these operations work.

What are the multiples of 10?

Multiples of 10 are numbers that can be divided evenly by 10. These numbers end in zero and include 10, 20, 30, 40, 50, and so on. When working with multiples of 10, you can think of them as a type of 'bigger number' that puts smaller numbers together into sets of 10.

Multiples of 10: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110...

Addition with multiples of 10

Adding multiples of 10 is similar to regular addition, but it involves numbers ending in zero. When adding these numbers, the tens digit increases while the units digit remains zero. Let us understand this with an example:

Example: Adding 20 + 30

When we add 20 and 30, we can think of adding the tens digit. Here, the tens digit of 20 is 2 and the tens digit of 30 is 3.

20 + 30 ----- 50

In the above example, when adding the tens digits we get: 2 + 3 = 5 The sum is 5, and since these are multiples of 10, we add a zero at the end, resulting in the final answer: 50.

Let's look at this visually:

203050

In the graphic above, each colored block represents a multiple of 10. The orange block represents 20, while the light blue block represents 30. When they are combined, they each complete once and come together to form a new length representing 50.

Subtracting by multiples of 10

Subtracting multiples of 10 also follows this pattern, primarily working with the tens digit while the ones digit remains zero. Here's how to think about subtraction using an example:

Example: Subtract 70 - 40

In this example, we start by focusing on the tens digit:

70 - 40 ----- 30

Subtract the tens digits: 7 - 4 = 3 As with addition, we add a zero to the end of our result with multiples of 10, resulting in 30.

Let's look at this example visually:

704030

Here, the light green block represents 70, and the red block we are subtracting represents 40. The resultant block, which remains green, represents the subtraction result of 30.

Understanding zero

An important part of working with multiples of 10 is understanding the role of zero. When you work with numbers that end in zero, it simplifies the calculation process. In 20 + 30, you focus on the 2 and 3, then add a zero. With 70 - 40, you focus on the 7 and 4, then add a zero.

Real-world applications

The ability to quickly add and subtract multiples of ten is a practical skill. Imagine you have 40 apples and you find 30 more. Quickly estimating that you now have 70 apples is an everyday example. Alternatively, if you have 90 pencils and you give away 50, it is helpful to know that you now have 40 pencils left.

Initial apples = 40 Received apples = 30 Total apples = 40 + 30 = 70 Initial pencils = 90 Given away pencils = 50 Remaining pencils = 90 - 50 = 40

Practice exercises

Practice makes perfect! Here are some exercises to see if you can easily add and subtract multiples of 10. Try solving each of these problems on your own or with a friend.

Yoga problems

1. 30 + 40 = ? 2. 50 + 20 = ? 3. 60 + 80 = ?

Subtraction problems

1. 90 - 60 = ? 2. 70 - 30 = ? 3. 100 - 50 = ?

Discovering patterns

An essential aspect when dealing with multiples of 10 is to recognize patterns. Notice that each increase or decrease usually involves the tens place. Consider which numbers remain constant and how the total number changes with the order of ten.

Patterns in addition and subtraction

Adding 10: 20 + 10 = 30 30 + 10 = 40 40 + 10 = 50 Subtracting 10: 50 - 10 = 40 40 - 10 = 30 30 - 10 = 20

This pattern recognition not only helps in understanding basic arithmetic, but also helps in developing mental mathematical strategies, which aid in more complex calculations.

Conclusion

Addition and subtraction with multiples of ten provide a foundational skill for students. These operations develop number sense and build confidence when working with numbers. By practicing these essential concepts through visual models and various exercises, students can effectively internalize how to handle multiples of ten in both mathematical contexts and everyday tasks.


Grade 2 → 1.3.6


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Addition and Subtraction with Multiples of 10

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