Strengthening Number Sense

Curriculum Area and Standard

Mathematics – Grade 2
Aligned to South Carolina College- and Career-Ready Standards for Mathematics
Standard: 2.ATO.1 – Add and subtract fluently through 99 using knowledge of place value and properties of operations.

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Lesson Objectives

By the end of this 30-minute session, students will be able to:

1. Use place value knowledge to add and subtract two-digit numbers fluently.
2. Apply properties of operations (commutative, associative, and identity properties) to solve addition and subtraction problems.
3. Mentally strategize ways to break numbers apart for efficient calculations.

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Materials Needed

• Place value blocks (tens and ones)
• Mini whiteboards and markers
• Number cards (10-99)
• Dice (1-6)
• Small toy coins or counters

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Lesson Structure

1. Warm-Up Activity: "Jump to 99!" (5 minutes)

Objective: Activate prior knowledge with a quick movement-based math game.

• Students stand up and start at zero.
• Teacher rolls two dice, and students add the sum to their total mentally.
• Continue rolling until a student reaches 99 exactly.
• Then, switch to subtraction—students move downward from 99 to zero.
• Discuss strategies they found helpful (e.g., breaking numbers into tens and ones).

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2. Guided Practice: "Place Value Puzzle" (10 minutes)

Objective: Reinforce place value to support fluent addition and subtraction.

• Each student picks two number cards (e.g., 47 and 26).
• Using place value blocks, they physically build the numbers.
• Then, they add or subtract by regrouping (if necessary):
  • Breaking apart tens and ones
  • Demonstrating the process using blocks
  • Writing the equation on their whiteboard

Example exchange:
🟩 "If we subtract 26 from 47, do we need to borrow from the tens?"

Challenge Question: Can they solve the same problem in a different way? (E.g., breaking numbers apart first into tens and ones before subtracting.)

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3. Interactive Game: "Operation Mystery!" (10 minutes)

Objective: Apply problem-solving skills using number flexibility.

• Each student draws a secret number card (e.g., 54).
• Teacher gives an operation card (addition or subtraction).
• Students roll a die to determine how much they will add/subtract.
• They then solve the problem mentally or with place value strategies.
• After solving, they explain their thinking aloud using math vocabulary.

🟨 Example conversation:
Teacher: "What is 54 minus 3?"
Student: "I kept 50 and took 3 away from the 4. That left me with 51!"

Extension: Ask them to prove their answer with another method (e.g., using number lines, blocks, or mental strategies).

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4. Wrap-Up Reflection: "Math Detective Chat" (5 minutes)

Objective: Encourage critical thinking and meta-cognition.

• Ask each student to describe a strategy they liked best.
• Have them reflect:
  • What was easy?
  • What was tricky?
  • What would they try next time?
• For fun, let them "teach" the teacher a problem using their own strategy!

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Differentiation (For Varying Abilities)

🔹 For students who need extra support:

• Use number lines or hands-on counters.
• Break down problems into even smaller steps.

🔹 For students ready for a challenge:

• Use three-digit numbers to extend thinking.
• Reverse the process—ask them to create their own word problems for a partner.

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Assessment Strategies

✅ Observation: Are students confidently explaining their strategies?
✅ Mini-whiteboard checks: Can they solve problems without needing blocks?
✅ Exit Ticket: One small addition/subtraction problem solved mentally & explained.

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Teacher Reflection

• Which strategies were most effective?
• Did students struggle with any concepts?
• How will this inform the next lesson?

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Closing Thought

This lesson goes beyond rote memorization—students see, feel, and explain math, fostering deeper number sense. With small adjustments, it can be made even more exploratory for young learners! 🌟