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Round and Roll!

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Kelsey Zimmerman

Tier 1
For Schools

Lesson Plan

Round and Roll!

Students will be able to confidently round two-digit and three-digit numbers to the nearest 10 and 100.

Rounding helps us estimate and make quick calculations in everyday life, like figuring out if you have enough money or how long something might take. Mastering this skill makes numbers more manageable and builds a strong foundation for more complex math.

Audience

3rd Grade Students

Time

30 minutes

Approach

Interactive review, visual aids, and hands-on practice.

Materials

Whiteboard or projector, Markers or pens, Rounding Mountain Slide Deck, Number Line Noodlers Activity, Rounding Practice Sheet, Rounding Answer Key, and Exit Ticket: Rounding Check-in

Prep

Teacher Preparation

10 minutes

  • Review the Rounding Mountain Slide Deck and familiarize yourself with the content.
    - Print copies of the Number Line Noodlers Activity (one per student or pair).
    - Print copies of the Rounding Practice Sheet (one per student).
    - Prepare the Rounding Answer Key for quick checking.
    - Print copies of the Exit Ticket: Rounding Check-in (one per student).
    - Ensure whiteboard or projector is ready.

Step 1

Warm-up: What's Your Closest Neighbor?

5 minutes

  • Project or write a few two-digit numbers on the board (e.g., 23, 48, 75).
    - Ask students: "Which 'friendly' number ending in zero is each of these numbers closest to?"
    - Briefly discuss their reasoning. This activates prior knowledge of number sense and proximity.

Step 2

Introduction: The Rounding Mountain Adventure

8 minutes

  • Introduce the concept of rounding using the Rounding Mountain Slide Deck.
    - Explain the 'mountain' analogy for rounding to the nearest 10: numbers 1-4 slide down, numbers 5-9 climb up.
    - Show examples on the slides for rounding to the nearest 10.
    - Transition to rounding to the nearest 100, explaining the same 'mountain' rule but with tens digits (0-49 slide down, 50-99 climb up).
    - Use interactive questions from the slide deck to check for understanding.

Step 3

Activity: Number Line Noodlers

10 minutes

  • Distribute the Number Line Noodlers Activity.
    - Explain that students will draw their own number lines and place numbers to visually see which 10 or 100 they are closest to.
    - Model one example for rounding to the nearest 10 and one for rounding to the nearest 100 on the board.
    - Circulate and provide support as students work individually or in pairs.

Step 4

Practice: Rounding Practice Sheet

5 minutes

  • Distribute the Rounding Practice Sheet.
    - Students will complete a few practice problems independently.
    - Review answers together using the Rounding Answer Key as a class or have students self-check.
    - Address any common misconceptions.

Step 5

Cool-down: Rounding Check-in

2 minutes

  • Distribute the Exit Ticket: Rounding Check-in.
    - Students quickly answer 1-2 rounding questions.
    - Collect as an exit ticket to assess individual understanding and identify students who may need further support.
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Slide Deck

Welcome to Rounding Mountain!

Our Goal Today:

  • Learn how to make numbers 'friendly'
  • Round numbers to the nearest 10
  • Round numbers to the nearest 100

Let's get ready for an adventure!

Welcome students and introduce the idea of 'friendly numbers.' Ask them what they think rounding means in simple terms.

Rounding to the Nearest 10: The Mountain Rule

When we round to the nearest 10, we look at the ones digit.

  • If the ones digit is 0, 1, 2, 3, or 4, the tens digit stays the same. (Slide down the mountain!)
  • If the ones digit is 5, 6, 7, 8, or 9, the tens digit goes up by one. (Climb up the mountain!)

All other digits after the tens place become zero.

Explain the concept of 'rounding to the nearest 10.' Use a number line as a visual. Introduce the 'mountain' analogy: if you're on the left side of the peak (1, 2, 3, 4), you roll down. If you're on the right side (5, 6, 7, 8, 9) or at the peak, you climb up.

Let's Practice Rounding to the Nearest 10

Example 1: Round 32 to the nearest 10

  • Ones digit is 2. (Slide down!)
  • 32 rounds to 30.

Example 2: Round 67 to the nearest 10

  • Ones digit is 7. (Climb up!)
  • 67 rounds to 70.

Example 3: Round 45 to the nearest 10

  • Ones digit is 5. (Climb up!)
  • 45 rounds to 50.

Go through these examples step-by-step. Ask students to identify the ones digit and decide if it rounds up or down. Engage them by asking 'Slide down or climb up?'

Rounding to the Nearest 100: A Bigger Mountain!

When we round to the nearest 100, we look at the tens digit.

  • If the tens digit is 0, 1, 2, 3, or 4, the hundreds digit stays the same. (Slide down the big mountain!)
  • If the tens digit is 5, 6, 7, 8, or 9, the hundreds digit goes up by one. (Climb up the big mountain!)

All other digits after the hundreds place become zero.

Now, introduce rounding to the nearest 100. Emphasize that the rule is similar, but we look at the tens digit. Use a different part of the mountain or a larger mountain analogy.

Practice Rounding to the Nearest 100

Example 1: Round 140 to the nearest 100

  • Tens digit is 4. (Slide down!)
  • 140 rounds to 100.

Example 2: Round 280 to the nearest 100

  • Tens digit is 8. (Climb up!)
  • 280 rounds to 300.

Example 3: Round 350 to the nearest 100

  • Tens digit is 5. (Climb up!)
  • 350 rounds to 400.

Work through these examples. For 140, highlight the tens digit (4) and explain why it rounds down. For 280, highlight the tens digit (8) and explain why it rounds up. For 350, highlight the tens digit (5) and explain why it rounds up.

Quick Check!

What does 76 round to the nearest 10?




What does 420 round to the nearest 100?




Pose a quick check for understanding. Ask students to share their answers and explain their reasoning. This helps reinforce the rules.

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Activity

Number Line Noodlers Activity

Instructions: For each number below, draw a number line. Mark the two tens (or hundreds) that the number falls between. Then, place the number on your number line and circle the nearest 10 or 100.

Rounding to the Nearest 10

  1. Number: 57







    57 rounds to:


  2. Number: 83







    83 rounds to:


  3. Number: 25







    25 rounds to:


Rounding to the Nearest 100

  1. Number: 130












    130 rounds to:


  2. Number: 680












    680 rounds to:


  3. Number: 450












    450 rounds to:


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Worksheet

Rounding Practice Sheet

Instructions: Round each number to the nearest 10 or 100 as specified.

Part 1: Round to the Nearest 10

  1. 43 rounds to:


  2. 78 rounds to:


  3. 12 rounds to:


  4. 95 rounds to:


  5. 61 rounds to:


  6. 39 rounds to:


Part 2: Round to the Nearest 100

  1. 170 rounds to:


  2. 320 rounds to:


  3. 890 rounds to:


  4. 550 rounds to:


  5. 240 rounds to:


  6. 760 rounds to:


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Answer Key

Rounding Answer Key

Number Line Noodlers Activity - Answers

Rounding to the Nearest 10

  1. Number: 57

    • Thought Process: 57 is between 50 and 60. The ones digit is 7, which is 5 or greater, so we round up.
    • 57 rounds to: 60

  2. Number: 83

    • Thought Process: 83 is between 80 and 90. The ones digit is 3, which is less than 5, so we round down.
    • 83 rounds to: 80

  3. Number: 25

    • Thought Process: 25 is exactly in the middle of 20 and 30. The ones digit is 5, so we round up.
    • 25 rounds to: 30

Rounding to the Nearest 100

  1. Number: 130

    • Thought Process: 130 is between 100 and 200. The tens digit is 3, which is less than 5, so we round down.
    • 130 rounds to: 100

  2. Number: 680

    • Thought Process: 680 is between 600 and 700. The tens digit is 8, which is 5 or greater, so we round up.
    • 680 rounds to: 700

  3. Number: 450

    • Thought Process: 450 is exactly in the middle of 400 and 500. The tens digit is 5, so we round up.
    • 450 rounds to: 500

Rounding Practice Sheet - Answers

Part 1: Round to the Nearest 10

  1. 43 rounds to: 40 (ones digit 3, rounds down)
  2. 78 rounds to: 80 (ones digit 8, rounds up)
  3. 12 rounds to: 10 (ones digit 2, rounds down)
  4. 95 rounds to: 100 (ones digit 5, rounds up - carries over to hundreds)
  5. 61 rounds to: 60 (ones digit 1, rounds down)
  6. 39 rounds to: 40 (ones digit 9, rounds up)

Part 2: Round to the Nearest 100

  1. 170 rounds to: 200 (tens digit 7, rounds up)
  2. 320 rounds to: 300 (tens digit 2, rounds down)
  3. 890 rounds to: 900 (tens digit 9, rounds up)
  4. 550 rounds to: 600 (tens digit 5, rounds up)
  5. 240 rounds to: 200 (tens digit 4, rounds down)
  6. 760 rounds to: 800 (tens digit 6, rounds up)
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Cool Down

Exit Ticket: Rounding Check-in

Instructions: Answer the questions below to show what you learned about rounding today!

  1. Round 63 to the nearest 10.



  2. Round 278 to the nearest 100.



  3. Why is rounding a useful skill in real life? Give one example.






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