6.GR.1 Lesson 5-2-group1 🟡 Group 1 · Set B
MASTERY CHECK
☐ Exceeds☐ Meets Target☐ Needs Practice

5.2 Small Group · Group 1

Second Practice Form · Re-Teach, Homework or Retake · Same Standard, New Problems

Area of a Triangle · Base · Procedural Fluency · Real-World Applications

Interactive Workbench & Models →
Name: Date: Period: Learning Goal:
■ CONCEPT SUMMARY & GUIDED NOTES: Let's build it together — How do we find the area of a triangle?
1Area of a triangle = ½ × base × height. A triangle is exactly half of a rectangle with the same base and height.
  • A triangle has three sides. The base is one side, and the height is the straight-up (perpendicular) distance from the base to the top corner. 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. My triangular garden has a base of 12 feet and a height of 8 feet.
  2. I write the formula: A = ½ × base × height.
  3. I put in the numbers: A = ½ × 12 × 8.
  4. I multiply base × height first: 12 × 8 = 96.
  5. I take half: ½ × 96 = 48. So the area is 48 square feet.
3Mathematical Word Bank
  • Area of a Triangle (Área de un triángulo) — The space inside a triangle. A triangle is half of a rectangle with the same base and height, so A = ½ × b × h.
  • Base (Base) — Any side of a triangle can be the base. Once you pick a base, the height must be measured perpendicular (at a 90° angle) to it.
  • Height (Altura) — The straight-up distance from the base to the top corner.
  • Area (Área) — How much space is inside a flat shape.
  • Perpendicular (Perpendicular) — Two lines that meet to make a square corner (90 degrees).
  • Composite figure (Figura compuesta) — A shape made by putting two or more simple shapes together.
4Watch out
  • A common mistake in Area of Triangles is forgetting the ½ — students multiply base × height like a rectangle and stop there, or they use the triangle's slanted side instead of the perpendicular height that's already given. Always check: did I take half, and did I use the straight-up height, not the slanted side?
SECTION 1 REAL-WORLD CONTEXTS & PROBLEM SOLVING [Applications]
  1. 1 MULTIPLE CHOICE

    A triangular window in the firm's lobby has a base of 10 ft and a height of 6 ft. What is its area?

    1. A30 sq ft
    2. B60 sq ft
    3. C16 sq ft
    4. D32 sq ft
    Formula
    Put the numbers in
    Work it out
    Answer with its unit
    1. 1Name itWhich measure is asked?
    2. 2Write the formulaBefore any numbers.
    3. 3SubstituteMatch each letter.
    4. 4Unitunits, sq units, or cubic?
  2. 2 MULTIPLE CHOICE

    A triangular roof panel on the blueprint has a base of 7 ft and a height of 4 ft. What is its area?

    1. A14 sq ft
    2. B28 sq ft
    3. C11 sq ft
    4. D22 sq ft
    Formula
    Put the numbers in
    Work it out
    Answer with its unit
    1. 1Name itWhich measure is asked?
    2. 2Write the formulaBefore any numbers.
    3. 3SubstituteMatch each letter.
    4. 4Unitunits, sq units, or cubic?
  3. 3 MULTIPLE CHOICE

    On the blueprint, a triangular garden bed has a base of 11 ft and a height of 6 ft. What is its area?

    1. A33 sq ft
    2. B66 sq ft
    3. C17 sq ft
    4. D30 sq ft
    Formula
    Put the numbers in
    Work it out
    Answer with its unit
    1. 1Name itWhich measure is asked?
    2. 2Write the formulaBefore any numbers.
    3. 3SubstituteMatch each letter.
    4. 4Unitunits, sq units, or cubic?
SECTION 2 MATHEMATICAL WRITING & ERROR ANALYSIS [Reasoning & Critique]
  1. 4 ERROR ANALYSIS

    Spot the Common Mistake

    1. 1Identify base and height:base = 9 ft, height = 4 ft
    2. 2Write the formula:A = ½ × base × height
    3. 3Multiply base × height:9 × 4 = 36
    4. 4Final answer:A = 36 sq ft

    Which step contains the error? Explain the mathematical misconception and write the correct calculation below.

    ✏️ Corrected Mathematical Work & Explanation
  2. 5 ERROR ANALYSIS

    Level 2 Extension — Find the Half-Area Mistake

    1. 1Identify base and height:base = 16 ft, height = 9 ft
    2. 2Write the formula:A = ½ × base × height
    3. 3Multiply base × height:16 × 9 = 144
    4. 4Final answer:A = 144 sq ft

    Which step contains the error? Explain the mathematical misconception and write the correct calculation below.

    ✏️ Corrected Mathematical Work & Explanation
  3. 6 ERROR ANALYSIS

    Find the Area Error

    1. 1Identify base and height:b = 14 m, h = 9 m
    2. 2Write the formula:A = ½ × b × h
    3. 3Substitute values:A = ½ × 14 × 9
    4. 4Calculate:A = ½ × 23 = 11.5 sq m

    Which step contains the error? Explain the mathematical misconception and write the correct calculation below.

    ✏️ Corrected Mathematical Work & Explanation
📐 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