Regroup to Add

Overview

This is lesson 13 of 18 in Math Explorers: Measure, Graph, Solve. Students build on place-value understanding to add within 1,000 by trading 10 ones for 1 ten and 10 tens for 1 hundred. They first use base-ten blocks, then connect each trade to a written addition strategy.

Learning intentions

Students will be able to:

• Explain what regroup means in addition.
• Trade 10 ones for 1 ten and 10 tens for 1 hundred.
• Add two- and three-digit numbers within 1,000.
• Use place-value tools and written work to find a sum.

Success criteria

• I can trade 10 ones for 1 ten or 10 tens for 1 hundred.
• I can line up ones, tens, and hundreds in boxed columns.
• I can use arrows to show each trade.
• I can find the correct sum in at least 4 of 5 examples.

Curriculum links

• Georgia Grade 2 Mathematics: add within 1,000 when 10 ones or 10 tens are regrouped.
• Number and Operations in Base Ten: use place value to connect concrete models with written addition.
• Measurement and Data: use addition and subtraction strategies for problems involving quantities and lengths given in the same units.

Lesson structure (30 minutes)

1. 0–4 min · Hook and connect. Teacher opens the hook and learning-intention slides and displays 8 ones and 7 ones, asking, “Can we make a new ten?” Students build or sketch the ones, predict the total, and share that 15 ones can become 1 ten and 5 ones.

2. 4–11 min · Teacher model. Teacher uses base-ten blocks to model 268 + 157, naming the vocabulary regroup, trade, carry, sum, ten, and hundred. Students build both numbers, combine the ones, physically trade 10 ones for 1 ten, then combine the tens and trade 10 tens for 1 hundred while following the recording on the place-value modeling slides.

Record the work in boxed columns:

2 hundreds 6 tens 8 ones
+ 1 hundred 5 tens 7 ones

Explain that “carry” is another word sometimes used for recording a regrouped unit, but the trade always keeps the value equal.

3. 11–17 min · Guided trading. Teacher displays the digital trade box on the guided practice slides and leads one place at a time, using a “stop and check” after each place. Students drag or physically move 10 ones into a trade box, replace them with 1 ten, and repeat with tens when needed. Pause to ask: “What did we trade? What is the value of the trade? Where does the new unit go?”

4. 17–25 min · Partner practice. Teacher distributes the regrouping practice mat and supports the three students as they solve four problems: two with base-ten blocks and two on the scaffolded written mat. Students use blocks for 146 + 178 and 235 + 186, then use boxed columns and trade arrows for 324 + 158 and 407 + 286. Teacher checks each place before students move on and prompts them to explain the value of every trade.

5. 25–28 min · Explain and correct. Teacher returns to the discussion and error-analysis slides and shows a common error, such as writing 15 in the ones place without regrouping. Students identify the error, correct it with blocks or a drawing, and explain why 10 ones must be traded for 1 ten.

6. 28–30 min · Exit assessment. Teacher gives each student the five-question check below, reading the questions and answer choices aloud as needed. Students may answer verbally, point to choices, or write.

7. Ten ones can be traded for… A. 1 ten B. 1 hundred C. 10 hundreds

8. 8 ones + 7 ones makes… A. 5 ones B. 15 ones C. 1 one

9. 268 + 157 =… A. 415 B. 425 C. 325

10. Regrouping means… A. trade equal value B. erase a number C. measure feet

11. Ten tens make… A. 1 hundred B. 1 ten C. 100 hundreds

Correct answers: 1-A, 2-B, 3-B, 4-A, 5-A.

Resources

• Base-ten blocks: ones, tens, and hundreds
• Place-value mats with boxed hundreds, tens, and ones columns
• the addition and regrouping slide deck
• the regrouping practice mat
• Pencils, crayons, or highlighters
• Five-question exit assessment
• Small trade box labeled “10 units become 1 new unit”

Assessment

• During modeling and guided practice, listen for students using “trade” and explaining that the value stays equal.
• Check whether students correctly regroup at the ones and tens places on the practice mat; use a stop-and-check after each place.
• Use the five-question exit assessment. A score of 4 or 5 shows the success criterion is met; students scoring below 4 should receive additional concrete practice with smaller numbers.

Differentiation

• Support: Begin with smaller examples such as 28 + 17. Use physical blocks, arrows showing each trade, boxed columns, and a place-value mat. Read every direction aloud and model one step at a time.
• Dyslexia-friendly access: Use a clear sans-serif font, large spacing, minimal text, color or shading for each place-value column, and consistent arrow symbols. Allow students to listen to questions, explain answers verbally, or point to an answer.
• Teacher prompting: Ask, “How many ones do you have?” “Can you make a ten?” and “Where does the traded ten go?” Provide immediate feedback before students continue.
• Extension within the activity: Invite a ready student to solve one problem without blocks, then prove the answer using blocks or an expanded-place-value drawing.