February 22, 2019
By April Brown

EL Support Lesson

Adding Within 20

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This lesson can be used as a pre-lesson for the Addition: Over in a FlashLesson plan.
GradeSubjectView aligned standards
This lesson can be used as a pre-lesson for the Addition: Over in a FlashLesson plan.

Students will be able to fluently add within 20.


Students will be able to explain how to find two addends that equal a given sum with more complex sentences using partnerships and sentence frames for support.

(3 minutes)
  • Bring the students together in a comfortable space and pass out personal whiteboards and markers to each student.
  • Write a number on the whiteboard within 20 (e.g. 10, 15, 12, etc). Explain to the students that this number represents a WholeAmount of banana muffins. Ask the students to think-pair-share with an elbow partner about how they could split the whole amount of muffins into two Parts. Give students a few minutes to think of their ideas and instruct them to jot them down on their whiteboards.
  • Allow a few students to share out their ideas. Ideas may include: 10 and 10, 13 and 7, 12 and 8, etc.
  • Explain to the students that the two parts are called AddendsIn addition, which simply means the numbers being added together.
  • Point to the number 20 and explain to the students that 20 is the Sum, or the total amount. When we add both addends together, we get the sum.
  • Explain that today they will explain how to find two addends that equal a given sum.
(10 minutes)
  • Put the students in partnerships and pass out a set of the Vocabulary Cards to each pair. Explain to the students that before they start the activity, they are going to learn some important words that will help them understand the goal of today's lesson.
  • Read through the student-friendly definitions, asking for student volunteers to help read the definitions as appropriate.
  • Explain that you want them to think of a visual that corresponds to each vocabulary word.
  • Model how to create a visual for one of the vocabulary words, using coloring materials to make the visual interesting and unique.
  • Clarify any questions before allowing students to get started in their partnerships. Rotate around the room and support students as necessary.
  • Allow each partnership to share 1–2 of their favorite visuals.
  • Provide the following sentence frame to support students in sharing why they chose to draw their visuals:
    • We chose to draw ____For ____(vocabulary word) because ____. Another idea we had was ____.
(8 minutes)
  • Keep students in partnerships and write another number on the board within 20. Make sure to choose a different number than the number used during the introduction.
  • Project the Part Part Whole worksheet on the whiteboard and get out the unifex or snap cubes.
  • Say, "I want to find as many combinations of addends as I can that equal the sum I wrote on the whiteboard. First, I'm going to count out ____Cubes (count the cubes one by one). Next, I'm going to separate the cubes into two parts (model separating the cubes and counting each set of cubes one by one). Finally, I'm going to record my answer using this graphic organizer. I'll write the WholeAmount in the bottom rectangle. Then I'll record the PartsIn each of the separate rectangles above the bottom rectangle."
  • Refer to the word bank on the bottom of the worksheet and model how to find the corresponding numbers in written form. Next, record the written numbers underneath your work.
  • Pass out unifex cubes to each partnership and challenge them to figure out a different combination of addends that equal the sum written on the whiteboard.
  • Allow a few partnerships to share out and record their answers on the Part Part Whole worksheet. Provide sentence frames to support students as they share out their ideas, such as:
    • ____And ____Is also ____. I know this because ____.
  • Encourage students to agree/disagree with their peers' ideas, and use active questioning techniques to challenge students to justify their reasoning (e.g. showing their solutions with cubes, drawings, etc.)
(10 minutes)
  • Pass out copies of the Part Part Whole worksheet to each partnership.
  • Write a number within 20 on the whiteboard that you have not yet used.
  • Give students five minutes to find as many combinations of addends they can that equal the sum on the whiteboard.
  • Encourage students to use the word bank to complete the sentence frames in each part-part whole combination. Instruct students to read the finished sentence frames aloud to their partners.


  • Provide students with written numbers in English and their home language (L1).
  • Pair students with a partner who speaks the same L1, if possible.
  • Review the concept of addition using manipulatives and real-world context.


  • Allow students to play the Bubble Buster: Addition to 20 game with partnerships. Encourage them to jot down as many combinations of addends that equal the given sum in their maths journals.
  • Encourage students to detail the steps of figuring out two parts of the whole using sequencing words.
  • Challenge students to share their ideas without referring to the sentence stems/frames for support.
  • Observe students as they are working and ask them to explain the process they used for figuring out the parts of the whole.
  • Jot down observations about collaboration, students' ability to discuss their ideas with partners, and general ability to agree or disagree with their partner's solutions in a productive way.
  • Make note of students who rely heavily on the cubes during group work. Also make note of students who fluently figure out the parts of the whole by relying on their knowledge of addition facts within 20.
(3 minutes)
  • Choose a few partnerships to share their answers with the rest of the class.
  • Compare and contrast answers, providing students with sentence frames to support their discussions:
    • I agree with ____Because ____. I would also add ____.
    • I disagree with ____Because ____. I would change it to ____.
  • Jot down as many different combinations as you can on the whiteboard.
  • Close the lesson by explaining to students that figuring out how to break numbers down into parts helps us learn our addition and subtraction facts better, especially the fact families, along with making our brains grow. Tell the students you are proud of the mathematicians they are becoming!

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