Addition and Subtraction

Objective

By the end of this 15-minute session, the student will be able to fluently add and subtract within 100, accurately solving problems with efficient strategies and understanding.

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Standards Alignment

CCSS.MATH.CONTENT.3.NBT.A.2
Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.

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Materials

• Whiteboard and marker
• Paper and pencil
• 10 counters/objects (for hands-on activity)
• Number cards 0-20

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Lesson Breakdown

1. Warm-up and Review (3 minutes)

• Begin with a quick oral review: Ask the student to solve some two-digit addition and subtraction problems mentally (e.g., 34 + 25, 50 - 18).
• Ask the student to explain the strategy they used (counting on, making ten, using place value). This primes their thinking for the upcoming activities.

2. Place Value Strategy Demonstration (4 minutes)

• Write a problem on the whiteboard, such as 46 + 27.
• Demonstrate decomposing numbers into tens and ones (40 + 6) + (20 + 7).
• Show how to add tens first (40 + 20 = 60), then ones (6 + 7 = 13), and combine the two sums (60 + 13).
• Use counters to physically show 13 as 10 + 3, exchanging 10 ones for 1 ten, reinforcing place value.
• Allow the student to try another example with support.

3. Interactive Number Card Game (5 minutes)

• Spread number cards 0-20 face down.
• Student draws two cards to create a two-digit addition or subtraction problem (e.g., 37 + 14 or 51 - 29, adjusting tens and ones as needed to stay within 100).
• Student uses paper to break down the problem by place value and solve it aloud.
• Teacher prompts student with questions such as “What strategy will you use? Can you explain your thinking?”

4. Quick Assessment and Reflection (3 minutes)

• Present 2 problems, one addition and one subtraction (e.g., 58 + 23 and 70 - 46).
• Ask the student to write down answers, showing the process step-by-step using place value strategies.
• Review answers together, providing positive feedback and reinforcing understanding.

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Differentiation

• For extra challenge, include problems that require regrouping (e.g., 67 + 29).
• For support, focus on smaller numbers with visual aids and manipulatives.

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Teacher Tips

• Celebrate every strategy used; explaining thinking should be valued as much as the final answer.
• Encourage the student to verbalize their understanding to deepen concept mastery.

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Summary

This quick, hands-on session engages the student through visual, verbal, and tactile strategies aligned to CCSS, building fluency in addition and subtraction within 100 through conceptual understanding and practice.