# Number Line Basics -- Adding and Subtracting

Learning how to use a number line when adding and subtracting is a first grade, Common Core math skill: 1.OA.5. 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.5 - Relate counting to addition and subtraction

Students who understand this principle can:

1. Represent addition and subtraction with tools such as base ten blocks, ten frames, number lines, and symbols.
2. Add by “counting all and counting on.”
3. Understand that, in an addition equation, one can count on from either number or “addend.”
4. Realize that +1 is the next number and that +2 is two numbers up in a number line.
5. Subtract by “counting back or counting on.”
6. Explain that, in a subtraction equation, one can either count back the value subtracted or count back until reaching the subtracted number (i.e. in 10-3, one can count back 3 times; in 10-3, one can count until 3).
7. Realize that -1 is the number prior and that -2 is two numbers prior in a counting sequence.

Video 1: Count to Add and Subtract with Miss D. Gunn

This video is a resource for teachers and parents that provides a brief example of an activity you can do with your students. The activity helps students connect the idea with counting to addition and subtraction.

Here is a list of suggested materials for the activity.

1. Index cards or whiteboards
2. Markers or pencils
3. Flashcards (with addition and subtraction problems).

Her first example is an addition problem: 3 + 7 = ?

1. Have students write the larger number first, then circle it.
2. Draw spaces equal to the smaller number.
a. So draw 3 spaces next to the 7.
b. ⑦ __  __  __
3. Students can either count on from the larger number or write in the following numbers.
4. The last number they write is the answer.
a. ⑦ 8   9   10

The second example shows how to use this method with a subtraction problem: 7 - 3 = ?

1. Write the first number first and circle it.
2. Draw spaces equal to the subtracted number.
a. ⑦ __  __  __
3. Count backwards by writing the numbers in the spaces or out loud.
a. ⑦ 6   5   4
4. The answer is the last number: 4.

Video 2: Using a Number Line to Add and Subtract

The video begins by reminding students of the basics of adding and subtracting by helping Jake count his library books.

Jakes likes to borrow books from the library and currently has 4 books. However, he needs more books for a project, and so Jake gets 3 more books. Boddle asks how many books he now has and uses a number line to find out.

1. Start at 4 on the number line since Jake started with 4 books.
2. Move to the right 3 times since Jake added 3 more books.
3. Counting 3 to the right, students should end at 7.
4. So, 4 + 3 = 7 books.

The video then goes into a subtraction example. The librarian reminds Jake that he needs to return 2 books. Boddle asks how many books will be left once Jake returns the 2 books and uses a number line.

1. Since Jake borrowed 7 books, start at 7 on the number line.
2. Move to the twice since he will be returning 2 books.
3. Counting 2 to the left, students should stop at 5.
4. So, 7 - 2 = 5 books.

The video ends by reminding students that, when using a number line, “Addition” means moving to the right, and “Subtraction” means moving to the left.

Want more practice?