Using Regrouping to Add

Introduction

• Write the problem 24 ________ 8 = ________ on the whiteboard. Represent the missing operation and difference with a blank circle or line. Say, "I'm making cupcakes for a party I'm going to this weekend. I told my friend I'd bring 24 cupcakes, and she said she had 8 cupcakes leftover from a party she went to last weekend. I want to make sure there are enough cupcakes to feed 30 people. How can I solve this problem?"
• Allow a student or two to share out their ideas about how to solve the problem. Guide them as they share out, and discuss whether the problem needs an addition sign or a subtraction sign. Encourage them to explain their reasoning by using some of the following prompts:
  • What do you mean by ________?
  • Can you tell me more about ________?
  • Can you give me an example of ________?
• Clarify that the addition sign is the correct choice because when we add, we figure out the sum of two or more numbers. Elaborate that the sum is the total amount from the addition of two or more numbers. Have students repeat after you, "When we add, we find the sum." Come up with a movement to support student understanding.
• Record the addition sign in the problem so it reads: 24 + 8 = ________. Next, put students into groups of four and provide whiteboards and whiteboard markers, base ten blocks, number lines, a hundreds chart, and manipulatives (e.g. beads, gems, stones, etc.) to each group of students.
• Tape the large anchor chart labeled "Addition Strategies" on the board.
• Discuss the addition strategies aloud with the students, referring to the visuals to increase student understanding. For example, say, "One way you can solve this addition problem is to draw a picture." Refer to the visuals on the anchor chart to support student understanding.
• Give students 2–3 minutes to solve the addition problem in their small groups. Instruct students to share the strategy they used out loud. Put a tally mark to the left of the anchor chart on the whiteboard to represent the strategy each group used.
• Explain to the students that each group used a strategy, or plan of action, to solve the problem. Explain that there are many different strategies we can use to solve addition problems. Say, "Today, we will learn about what it means to regroup and how regrouping with base ten blocks can help us when we solve addition problems."