6.NOS.3 Lesson 2-11-group1 🟡 Group 1 · Support & Scaffolding
MASTERY CHECK
☐ Exceeds☐ Meets Target☐ Needs Practice

2.11 Small Group · Group 1

Tier 2 Intervention · Concrete-Representational-Abstract (CRA) · Dual-Language Anchors

Visual Models · Add and Subtract Decimals · Decimal · Procedural Fluency

Interactive Workbench & Models →
Name: Date: Period: Learning Goal:
■ CONCEPT SUMMARY & GUIDED NOTES: Let's build it together — How do you add and subtract decimals?
1Line up the decimal points, add zeros so each number has the same number of decimal places, then add or subtract one column at a time.
  • A decimal is a number with a point that shows parts smaller than one whole. To add or subtract decimals, you line up the decimal points so the same place values match. We'll walk through a worked example, try one together, then you'll try a few with hints right there when you need them.
2Worked Example — Watch me
  1. The tank has 128.75 liters. A shuttle adds 46.8 liters. I line up the decimal points and annex a zero: 46.80.
  2. I add: 128.75 + 46.80 = 175.55 liters.
  3. Now the thrusters use 19.35 liters, so I subtract: 175.55 − 19.35 = 156.20.
  4. The final fuel level is 156.20 liters. I check with estimation: about 130 + 47 − 19 = 158, which is close, so my answer is reasonable.
3Mathematical Word Bank
  • Add and Subtract Decimals (Sumar y restar decimales) — Combine or find the difference between decimals by lining up equal place values.
  • Decimal (Decimal) — A number with a dot, like 0.5, that shows a part less than one.
  • Place value (Valor posicional) — What a digit is worth based on where it sits in a number.
  • Tenths (Décimas) — The first spot after the decimal point. It shows parts out of 10.
  • Hundredths (Centésimas) — The second spot after the decimal point. It shows parts out of 100.
  • Annex zeros (Agregar ceros) — Adding zeros at the end of a decimal so numbers line up evenly.
4Watch out
  • A common mistake in Add and Subtract Decimals is lining up the last digits (the right edges) of each number instead of lining up the decimal points — for example, adding 8.3 and 2.45 as if the 3 and the 5 belong in the same column. Before you add or subtract, add zeros so every number has the same number of decimal places (write 8.3 as 8.30), then check that the decimal points sit directly above one another.
SECTION 1 CONCEPTUAL UNDERSTANDING & VISUAL MODELS [Visual Modeling]
  1. 1 NUMBER LINE

    Show 6.5 − 2.8 and 3.25 + 1.5 on the number line

    ✏️ Workspace & Solution Steps
  2. 2 FILL TABLE

    Compute each decimal sum or difference.

    ProblemAnswer
    5.63 + 2.7
    12.4 − 8.56
    9.08 + 4.925
    25.1 − 13.47
    7.006 + 3.94
    ✏️ Scratchpad / Reasoning
SECTION 2 COMPUTATION & PROCEDURAL FLUENCY [Show Every Step]
  1. 3 MULTIPLE CHOICE

    What is 14.6 + 3.85?

    1. A18.45
    2. B18.35
    3. C17.45
    4. D18.55
    Line up the place values
    1. 1Line upPoints under points.
    2. 2Fill gapsWrite in the zeros.
    3. 3OperateRight to left.
    4. 4Bring the point downStraight down.
  2. 4 MULTIPLE CHOICE

    What is 9.05 + 4.7?

    1. A13.75
    2. B13.12
    3. C14.75
    4. D13.57
    Line up the place values
    1. 1Line upPoints under points.
    2. 2Fill gapsWrite in the zeros.
    3. 3OperateRight to left.
    4. 4Bring the point downStraight down.
SECTION 3 REAL-WORLD CONTEXTS & PROBLEM SOLVING [Applications]
  1. 5 MULTIPLE CHOICE

    What is 20.3 − 7.48?

    1. A12.82
    2. B13.82
    3. C12.92
    4. D12.18
    Line up the place values
    1. 1Line upPoints under points.
    2. 2Fill gapsWrite in the zeros.
    3. 3OperateRight to left.
    4. 4Bring the point downStraight down.
  2. 6 MULTIPLE CHOICE

    What is 50 − 23.47?

    1. A26.53
    2. B27.53
    3. C26.63
    4. D27.47
    Line up the place values
    1. 1Line upPoints under points.
    2. 2Fill gapsWrite in the zeros.
    3. 3OperateRight to left.
    4. 4Bring the point downStraight down.
🗣️ MATHEMATICAL DISCOURSE & TALK MOVES SMP.3 / Construct Viable Arguments

Group Discussion Prompt: How does your visual model justify your mathematical solution?

🗣️ Partner A:
Partner A: "I modeled this by identifying the relationship and..."
👂 Partner B:
Partner B: "I agree with your step because the standard mathematical rule states..."
✍️ The Writing Revolution (TWR) · Sentence Expansion Because · But · So

Complete each sentence stem to demonstrate precise mathematical reasoning:

BECAUSE The mathematical model proves the solution because each step preserves quantitative equivalence.
BUT An estimate provides a quick benchmark, but an exact proof is required for precision.
SO The quantities follow the standard rule, so the final result is verified with certainty.
📐 CER MATHEMATICAL PROOF MATRIX (CER 2.0) SMP.3 / Proof & Justification

Writing Task: Justify why your mathematical solution is accurate and complete.

C Claim
Starter: My mathematical claim is that the solution is...
E Evidence
Starter: The evidence from the model/table demonstrates that...
R Reasoning
Starter: This proves my answer because the standard mathematical definition of...
Student Mastery Self-Assessment:
1 · Need More Support
2 · Getting Closer
3 · Got It / Solid
4 · Master / Can Teach It