EL Support Lesson
Using Regrouping to Add
Students will be able to add a one-digit number to a two-digit number with regrouping.
Students will be able to describe what it means to regroup using base ten blocks and a sentence frame.
- 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."
Explicit Instruction/Teacher modeling(10 minutes)
- Take out base ten blocks (ones and tens), the Place Value Mat: Two-Digit Numbers worksheet (preferably laminated), and turn on the projector or document camera. On the paper, write 18 + 8, vertically. Make sure place values are aligned. Next, provide a real-life story about what the numbers represent so students can connect with the math problem.
- Say, "We are going to pretend that these numbers represent plates. I am having a party for 25 people at my house. I have 18 plates at my house. My friend is going to bring over 8 more plates. I want to make sure I have enough plates for 25 people. How can I solve my problem?"
- Instruct the students to share if you will need to add or subtract, based on the problem you shared and the symbol in the math problem. Provide the following sentence frame to support students as they share their ideas with an elbow partner:
- I think we need to ____ (add/subtract) because ____.
- Clarify that you will need to add. Say, "Who remembers what addition is?" Have students turn and talk to a partner, sharing their answer.
- Tell the students that you are going to solve the problem using the strategy of base ten blocks. Ask the students to put a thumbs up if they have ever used base ten blocks. Count out one group of ten and eight ones from the blocks. Make sure you count by ones and touch each block up to 18. Place the blocks in the correct column on the Place Value Mat. Next, explain to the students that you want to add, or combine, 8 with 18 to see if you have enough plates for 25 people.
- Count out eight more ones from the blocks and place them in a separate group on the Place Value Mat. Explain to the students that when you have ten or more ones, you can trade ten ones for one group of ten. Explain that regrouping in addition is when you trade 10 in one place value position for 1 in the position to the left.
- Count how many ones are now available. Say, "There are 16 ones." Continue by saying, "I'm going to get out ten ones. Next, I'm going to trade these ones for a group of ten." Make sure to count by ones up to 10 to reiterate that the group of tens represents ten ones. Place the group of tens on the tens side of the Place Value Mat. Say, "Now I have two groups of tens and six ones. Turn and talk to a partner, sharing how many plates I have altogether."
- Allow a student to share out their answer. Ask students if you have enough plates to feed 25 people. Encourage students to explain their reasoning.
Guided Practice(10 minutes)
- Put students into pairs and write the following addition problems with regrouping on the whiteboard (vertically with place values aligned):
- A) 16 + 7, B) 15 + 6 , C) 25 + 8, D) 35 + 8, E) 46 + 5, F) 54 + 7
- Pass out the Place Value Mat: Two-Digit Numbers worksheet and enough base ten blocks to effectively solve the problems.
- Explain to the students that they are going to solve the addition problems with their partner, using base ten blocks.
- Ask students to turn and talk to their partners, explaining the concept of regrouping. Reiterate that when we regroup in addition, we exchange 10 in one place value position for 1 in the position to the left. Today, this means exchanging ten ones for a group of ten.
- Encourage a student to explain regrouping in their own words.
- Have one partnership come up to the board to model solving one of the addition problems on the whiteboard. Guide them as they use the Place Value Mat and base ten blocks. Provide ample opportunities for students to share their thinking, guiding them to explain the concept of regrouping. Prompting questions include: "I see you have more than ten ones. What will you do next? How do you know how many ones are in one group of ten? One group of ten is the same as ____?"
- Ask students to go back to their seats and give students ten minutes to solve the addition problems on the whiteboard with their partners.
- Discuss answers aloud and ask students how they solved the problems. Use the following sentence frames to support students in sharing out:
- Solving the problems using base ten blocks was ____ (easy/okay/hard) because ____.
- Using base ten blocks helped/didn't help me because ____.
- I used a different strategy. The strategy I used was ____.
Group work time(10 minutes)
- Create two number banks on the whiteboard (two large squares). In the first number bank, write "Numbers on Top" above the number bank and write the following numbers inside: 15, 36, 55. In the second number bank, write "Numbers on the Bottom" above the number bank and write the following numbers inside: 7, 8, 9.
- Keep the students in partnerships and explain that they are going to make their own (co-craft) two-digit by one-digit addition problems. Provide students with personal whiteboards and whiteboard markers.
- Explain to the students that the goal is to create an addition problem that will involve regrouping.
- Tell the students that they will use the number banks to create their addition problems. Refer to the "Numbers on Top" number bank and explain that these numbers are two digits, so they will go on top. Point to the "Numbers on the Bottom" number bank and explain that these numbers are one digit, so they will go on the bottom. Model how to use the number banks to create an addition problem with regrouping.
- Explain to students that after they create their own addition problem on their whiteboards, they will solve it, using the strategy of base ten blocks. When they are finished, they will exchange problems with their partner and discuss how the strategy of the base ten blocks worked for them. Encourage them to also share any strategies they used that didn't involve the base ten blocks. Tell the students that if they get different answers, they should try to rework the problem again using the base ten blocks.
- Write the following sentence frames on the board to help students with in depth discussions:
- My partner and I used ____ (the same/different) strategies to solve the problems.
- My partner and I got ____ (the same/different) answers.
- After solving the problem again, I learned ____.
- Have one partnership share their ideas with the class.
Additional EL adaptations
- Review the concept of addition using manipulatives and real-world representations.
- Allow students to share out one answer during the assessment.
- Provide students with manipulatives to use when explaining regrouping during the assessment.
- Encourage students to verbally share their understanding of regrouping with the rest of the class.
- Have students compare/contrast their strategy with their partners' strategy during group work.
- Rotate around the room as students are solving the problems during group work. Record the names of students who demonstrate understanding of the learning objective and language objective. Observe students who are struggling, and write down what part of the process they are struggling with. For example, the procedure of regrouping itself, need another lesson on using base ten blocks, need more support in collaborating, understanding of directions, etc.
- Use observations as a formative assessment to help you plan and design future lessons on two-digit by one-digit addition with regrouping to best meet students' needs.
Review and closing(2 minutes)
- Write the following sentence frames on the board:
- Regrouping in addition means ____.
- Using base ten blocks made regrouping ____ (easier/harder).
- Have students do a think-pair-share, answering both questions.
- Refer to the Addition Strategies anchor chart and explain that using base ten blocks is just one way they can solve addition problems, including addition problems with regrouping!