# Adding Numbers up to 20

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.

Prior Learnings

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).

Future Learnings

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:

1. Use objects and/or drawings to represent and solve word problems that add three whole numbers.
2. Write equations that use the addition of three whole numbers to the unknown using a symbol.
3. Add three whole numbers whose sums are less than or equal to 20.

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.

1. Seven circles are drawn under 7 to represent the number.
2. Four circles are drawn under 4 to represent the number.
3. Five circles are drawn under 5 to represent the number.
4. To find how many circles there are in total, all three groups must be combined.
a. The speaker counts each circle, ending with 16.
5. So, “7 + 4 + 5 = 16.”

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.

1. The first fruits are apples.
a. There are 4 apples.
2. The next fruits are oranges.
a. There are 3 oranges.
3. The last fruits are strawberries.
a. There are 6 strawberries.
4. 4 apples + 3 oranges + 6 strawberries = 13 fruits.

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.

1. There are 4 toy cars.
2. There are 8 dolls.
3. There are 3 balls.
4. 4 + 8 + 3 = 15 toys in total.

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.

1. There are 6 yellow flowers.
2. There are 4 pink flowers.
3. 6 + 4 = 10.
4. Then, 7 new red flowers are planted.
5. The video asks what 7 + 10 equals.
6. There are now 17 flowers in total.

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