Learning to add numbers up to 20 is a first grade, Common Core math skill: 1.OA.2. Below we show two videos that demonstrate this standard. Then, we provide a breakdown of the specific steps in the videos to help you teach your class.
Your students should be familiar with the Kindergarten skill of understanding the number pairs that equal 10 and knowing all decompositions (e.g. 5=4+1, 5=2+3) of numbers below 10. This skill builds a foundation for strategy development, the understanding of place values, and properties of operations (K.OA.3-4). Your students should also understand that ten 1’s plus more 1’s are considered “teens” (K.NBT.1).
Understanding how to perform addition and subtraction within 20 will enable your students to perform similar skills up to 100, eventually extending those skills to work with larger numbers and solve two-step word problems (2.OA.1). They will also be able to apply this skill with problems in a variety of contexts involving length, picture graphs and bar graphs (2.NBT.5).
Common Core Standard: 1.OA.2 - Solve word problems that add three whole numbers whose sums are less than or equal to 20
Students who understand this principle can:
2 Videos to Help You Teach Common Core Standard: 1.OA.2
Below we provide and breakdown two videos to help you teach your students this standard.
Video 1: Combining Groups
The video starts by explaining that your students will learn how to add three numbers (whose values are less than 20).
The speaker reminds students that adding three numbers is the same as adding two, all you are doing is combining groups. The numbers added in the video are 7 + 4 + 5.
The video ends by reminding students that when adding three numbers together, simply combine the three groups to determine how many there are in total.
Video 2: Helping Irene Add Objects
The video begins by helping Irene count the fruit her mom just bought from the grocery store. They count the number of each type of fruit first, and then add the total of each group together.
Later, Boddle helps Irene count the number of toys in her room. She has toy cars, dolls, and balls. The number of toys in each group is counted, and then the totals for each group are added together.
Next, the video follows Irene to her backyard to help her count the number of flowers planted. The number of flowers in each group are counted and their totals added together.
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*Information on standards is gathered from The New Mexico Public Education Department's New Mexico Instructional Scope for Mathematics and the Common Core website.