Two-Digit Addition

Overview

Students will add a two-digit number and a one-digit number, and practice adding a two-digit number and a multiple of 10, using place value strategies and concrete drawings. They will connect the model strategy to a written number sentence and explain their reasoning.

Learning intentions

Students will be able to…

• Add within 100 using tens and ones (add tens to tens, ones to ones).
• Use concrete models or drawings to represent two-digit addition.
• Explain when it is necessary to compose (make) a ten during addition.
• Relate their model strategy to a written method and number sentence.

Success criteria

• I can show tens and ones to help me add accurately.
• I can add a one-digit to a two-digit by adding ones and regrouping if needed.
• I can add a multiple of 10 to a two-digit by adding tens.
• I can explain my steps using words like tens, ones, and compose a ten.

Curriculum links

• Number and Operations in Base Ten: add within 100 using concrete models/drawings and place value strategies; explain reasoning (including composing a ten).
• Operations and Algebraic Thinking: use strategies like making ten and connecting addition to written methods.
• Operations and Algebraic Thinking: apply properties of operations as strategies for equivalent/add-easier sums.

Lesson structure (15 minutes)

1. 0–2 min · Warm-up (Quick Talk). Teacher displays: “14 + 3” and asks, “What part is ones? What part is tens?” Students point to tens/ones using fingers or a quick sketch.
2. 2–6 min · Model it (Teacher-led). Teacher shows base-ten blocks or tens/ones drawings for 14 (1 ten rod + 4 ones cubes), then adds 3 more ones, counting on ones and making a ten if needed (e.g., 14 + 6 shows 4 ones + 6 ones makes 10 ones). Students watch and answer when prompted: “Did we compose a ten? What number of tens do we have now?”
3. 6–9 min · Guided practice #1 (Try it with support). Teacher gives a new problem: “23 + 4.” Teacher guides students to draw or build 23, add 4 ones, regroup into a ten if the ones sum reaches 10 or more, then record the equation. Students work together to complete model → written number sentence, and say one sentence explaining the strategy they used.
4. 9–12 min · Guided practice #2 (Multiple of 10). Teacher poses: “27 + 20.” Teacher points out only tens change; add tens to tens (2 tens + 2 tens) while ones stay the same. Students complete a model and write the sum.
5. 12–14 min · Fluency check (Two quick problems). Teacher shows two mini-card problems:

• “35 + 6” (may require composing a ten)
• “48 + 10” (tens-only addition) Students choose a strategy (draw, blocks, or counting on by tens/ones) and write each answer in a single sentence using tens/ones words.

6. 14–15 min · Exit ticket (Reasoning in one line). Students solve one prompt chosen by teacher (teacher selects based on pace): “Add 2 tens to 16” OR “Add 5 ones to 19.” Students respond with the equation and one explanation sentence: “I added ___ tens and ___ ones, so the sum is ___.”

Resources

• Base-ten blocks (tens rods and ones cubes) or two-color counters
• Place value mat (Tens column / Ones column)
• Student whiteboards or paper and pencils
• Problem cards for 14 + 3, 23 + 4, 27 + 20, 35 + 6, 48 + 10
• Recording sheet template: “Model → Equation → Explanation”
• Timer visible to teacher (to keep within 15 minutes)

Assessment

• During modeling (0–6 min): listen for correct identification of tens vs ones and whether students notice composing a ten.
• During guided practice (6–12 min): check that students write correct number sentences and can explain using tens/ones language.
• Exit ticket (14–15 min): verify accuracy of sums within 100 and that the explanation references place value strategy (tens/ones and composing if needed).

Differentiation

• Support: Provide sentence starters on the board: “I added ___ ones,” “I made a ten,” “So I have ___ tens and ___ ones.” Allow students to start with drawing if blocks are slow.
• Support for composing: If students struggle, teacher uses a “bundle of ten” visual (highlight 10 ones) to prompt regrouping before recording the final sum.
• Extension: If students finish quickly, ask them to solve the same problems two ways (e.g., model and counting on, or model and decomposing/making ten) and compare which is easier.
• EAL/SEN: Keep language consistent with tens/ones cues and use gestures (point to Tens column/Ones column). Use a smaller set of numbers first (e.g., 14 + 3, 20 + 7) if needed, then return to the target problems.