Build and Add

Overview

Students add three-digit numbers using place value and written regrouping. The teacher models one example, then guides brief practice on a slate or gridded worksheet so writing does not overtake the arithmetic. The final minutes review a multiplication-by-ten fact and check understanding.

Learning intentions

Students will be able to:

• Add three-digit numbers accurately.
• Use place value to explain regrouping.
• Record an addition problem in aligned columns.
• Check whether an answer is reasonable.

Success criteria

• I can line up ones, tens, and hundreds.
• I can regroup 10 ones as 1 ten and 10 tens as 1 hundred.
• I can explain how I found my answer.
• I can check my answer by estimating or using subtraction.

Curriculum links

• Number and Operations in Base Ten — fluently add and subtract within 1,000 using place-value strategies and algorithms.
• Operations and Algebraic Thinking — apply properties of operations as strategies to multiply.
• Number and Operations in Base Ten — multiply one-digit numbers by multiples of 10 using place value.
• Operations and Algebraic Thinking — identify and explain arithmetic patterns.

Lesson structure (10 minutes)

1. 0–2 min · Quick review and hook. Open the hook and review slides and ask, “Which is greater: 248 + 137 or 300?” Students estimate orally, then explain how they know without calculating exactly. Briefly review that numbers can be decomposed into hundreds, tens, and ones.

2. 2–4 min · Teacher model. Display 248 + 137 using the place-value modeling slide. Teacher models: add 8 ones and 7 ones to make 15 ones; write 5 ones and regroup 1 ten; add 4 tens, 3 tens, and the regrouped ten to make 8 tens; add the hundreds to make 385. Students watch, say the place-value language aloud, and show a finger when they identify a regrouping step.

3. 4–7 min · Guided practice. Give the student the three-digit addition practice sheet or write the problems on a slate. Using the guided-practice slide, solve 326 + 145 together, pausing after each column. Students align the numbers, solve from ones to hundreds, and explain where any regrouping occurs.

4. 7–8 min · Independent check. Point to the final problem on the three-digit addition practice sheet: 457 + 268. Students solve independently on gridded paper or a slate, using place-value drawings or expanded form if needed. Teacher observes alignment, regrouping, and whether the student records each digit in the correct column.

5. 8–10 min · Review and exit check. Return to the review and exit slide. Students answer 240 + 130 mentally, then complete an oral exit response: “I added the ___ place first because ___.” Teacher asks the student to estimate 457 + 268 and compare the estimate with the exact answer.

Resources

• the complete addition mini-deck
• the three-digit addition practice sheet
• Slate or dry-erase board
• Gridded paper
• Pencil or dry-erase marker
• Place-value chart or base-ten blocks
• Optional number cards for building hundreds, tens, and ones

Assessment

• During modeling and guided practice, check whether the student aligns place values and can describe regrouping as composing 10 ones into 1 ten or 10 tens into 1 hundred.
• Review the independent problem for accurate computation, correct column alignment, and a reasonable estimate.
• Use the final oral response as an exit ticket. If the student cannot explain the regrouping, reteach with base-ten blocks before assigning further practice.

Differentiation

• Support: Use a place-value chart or base-ten blocks and color-code the ones, tens, and hundreds columns. Provide one problem at a time and allow the student to solve orally before recording.
• Writing accommodation: Write problems on the slate or worksheet and let the student place or say digits rather than copy lengthy directions. Use wide-spaced, clearly printed numerals and a dyslexia-friendly sans-serif font.
• Language support: Offer sentence starters such as “I regrouped ___ ones because…” and “The ___ place has….” Say each number in expanded form before solving.
• Challenge: Ask the student to solve 326 + 145 using both the standard algorithm and expanded form, then explain why both methods produce the same sum.