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Algebraic Identity (a + b)³ 3D Dissection Model

Experiment video

What you will learn

Verify the algebraic identity (a + b)³ = a³ + 3a²b + 3ab² + b³ geometrically using a set of 8 physical 3D volumetric acrylic blocks of dimensions a and b.

Materials needed

  • 3D Acrylic / Wooden mathematical model set for binomial cube: a = 4 cm, b = 2 cm set
    3D Acrylic / Wooden mathematical model set for binomial cube: a = 4 cm, b = 2 cm set
    ₹50
    What is it?

    Montessori / CBSE standard 8-piece wooden Binomial Cube apparatus in hinged wooden box.

    Specifications
    Material
    Fine grain seasoned beechwood
    Dimensions
    a = 50 mm, b = 20 mm; assembled cube = 70 mm × 70 mm × 70 mm
    Color Coding
    Red (a³), Black with yellow edge (3a²b), Black with blue edge (3ab²), Blue (b³)
    Box
    Hinged wooden storage box with printed lid diagram
  • - Cube of side a (4 = 64 cm³) × 1
    NS
    - Cube of side a (4 = 64 cm³) × 1
    ₹95
    What is it?

    Digital Vernier Caliper for verifying block face dimensions.

    Specifications
    Resolution
    0.01 mm
    Accuracy
    ± 0.02 mm
  • - Cube of side b (2 = 8 cm³) × 1
    - Cube of side b (2 = 8 cm³) × 1
    ₹140
    What is it?

    Standard laboratory apparatus used in Algebraic Identity (a + b)³ 3D Dissection Model.

    Specifications
    Category
    Mathematics Apparatus
    Grade
    CBSE / NEP 2020 Laboratory Standard
  • - Cuboids of dimension a × a × b (4 = 32 cm³) × 3
    - Cuboids of dimension a × a × b (4 = 32 cm³) × 3
    ₹185
    What is it?

    Standard laboratory apparatus used in Algebraic Identity (a + b)³ 3D Dissection Model.

    Specifications
    Category
    Mathematics Apparatus
    Grade
    CBSE / NEP 2020 Laboratory Standard
  • - Cuboids of dimension a × b × b (4 = 16 cm³) × 3
    - Cuboids of dimension a × b × b (4 = 16 cm³) × 3
    ₹230
    What is it?

    Standard laboratory apparatus used in Algebraic Identity (a + b)³ 3D Dissection Model.

    Specifications
    Category
    Mathematics Apparatus
    Grade
    CBSE / NEP 2020 Laboratory Standard
  • Display tray with base 6 cm cm
    Display tray with base 6 cm cm
    ₹275
    What is it?

    Standard laboratory apparatus used in Algebraic Identity (a + b)³ 3D Dissection Model.

    Specifications
    Category
    Mathematics Apparatus
    Grade
    CBSE / NEP 2020 Laboratory Standard
  • Metric Vernier Caliper / Ruler
    Metric Vernier Caliper / Ruler
    ₹320
    What is it?

    Standard laboratory apparatus used in Algebraic Identity (a + b)³ 3D Dissection Model.

    Specifications
    Category
    Mathematics Apparatus
    Grade
    CBSE / NEP 2020 Laboratory Standard

Tick items as you collect them. Tap + to see the product, specifications and buy options.

Stay safe

  • Handle precision acrylic blocks carefully to avoid chipping corners and edges.
  • Ensure all 8 blocks fit together flush without gaps when building the main cube.
  • Label dimensions a and b clearly on each block face to facilitate spatial tracking.
  • Store blocks in labeled compartments to prevent losing components.

Steps

0 of 7 steps done
  • 1Measure dimensions of each block using a ruler: confirm a = 4 cm and b = 2 cm.
    Observation

    Unpack the 8 polished wooden sub-blocks of the binomial cube kit; identify distinct dimensions a = 5 cm and b = 2 cm.

    Safety

    Inspect wooden blocks for smooth polished corners without splinters.

  • 2Assemble all 8 blocks together inside the tray to form a large single solid cube.
    Observation

    Measure Block A (cube of side a = 5 cm); compute volume V = a³ = 5³ = 125 cm³.

    Safety

    Verify dimensions with Vernier caliper or metric ruler.

  • 3Measure the edge of the large assembled cube: edge = a + b = 4 + 2 = 6 cm.
    Observation

    Identify the 3 identical square prisms of base a × a (5×5 cm) and height b (2 cm); combined volume = 3a²b = 3 × 50 = 150 cm³.

    Safety

    Group blocks into matching sets by shape and color.

  • 4Calculate total volume of assembled cube: V = (a + b)³ = 6³ = 216 cm³.
    Observation

    Identify the 3 identical square prisms of base b × b (2×2 cm) and height a (5 cm); combined volume = 3ab² = 3 × 20 = 60 cm³.

    Safety

    Check that cross-sections align flush.

  • 5Disassemble the cube and separate into 4 component categories:
    Observation

    Measure Block D (small cube of side b = 2 cm); compute volume V = b³ = 2³ = 8 cm³.

    Safety

    Ensure all 8 components are accounted for.

  • 61 cube of a³ (volume = 64 cm³), 3 cuboids of a²b (volume = 3 × 32 = 96 cm³), 3 cuboids of ab² (volume = 3 × 16 = 48 cm³), 1 cube of b³ (volume = 8 cm³).
    Observation

    Assemble all 8 blocks inside the 7 cm cubic wooden box; they pack seamlessly into a single solid cube of side (a+b) = 7 cm (volume 343 cm³).

    Safety

    Close box lid to verify perfect flush fit without rattling or protruding.

  • 7Sum the volumes of all 8 components: 64 + 96 + 48 + 8 = 216 cm³. Confirm (a + b)³ = a³ + 3a²b + 3ab² + b³.

Tap + on a step to see what you will observe and any safety tips.

Record your observations

Component Block IdentityQuantity in SetAlgebraic DimensionsVolume per Block (cm³)Total Sub-Volume (cm³)
Block A (Large Cube)1 blocka × a × a (5 cm × 5 cm × 5 cm)a³ = 125.0 cm³125.0 cm³
Block B (Square Prism A)3 blocksa × a × b (5 cm × 5 cm × 2 cm)a²b = 50.0 cm³3 × 50.0 = 150.0 cm³
Block C (Square Prism B)3 blocksa × b × b (5 cm × 2 cm × 2 cm)ab² = 20.0 cm³3 × 20.0 = 60.0 cm³
Block D (Small Cube)1 blockb × b × b (2 cm × 2 cm × 2 cm)b³ = 8.0 cm³8.0 cm³
Total Composite Cube8 blocks total(a + b)³ = (5 + 2)³ = 7³ cm³(a + b)³ = 343.0 cm³125 + 150 + 60 + 8 = 343.0 cm³ (Exact match)

Tap a highlighted cell to write your own observation.

Result and conclusion

An assembled cube of side (a + b) decomposes into exactly 8 geometric solid pieces: 1 cube of a³, 3 cuboids of a²b, 3 cuboids of ab², and 1 cube of b³, verifying the identity.

(a + b)³ = a³ + 3a²b + 3ab² + b³ (Volume of Large Cube = Sum of Volumes of 8 Dissected Sub-Blocks)
ObservationWhat it means
Exact Spatial Volume ConservationSum of volumes of the 8 sub-blocks (125 + 150 + 60 + 8 = 343 cm³) exactly equals volume of assembled cube (7³ = 343 cm³).
Algebraic Binomial Expansion VerifiedPhysical assembly provides an unforgettable three-dimensional tactile proof of (a + b)³ = a³ + 3a²b + 3ab² + b³.
Geometric Significance of CoefficientsThe binomial coefficients 1, 3, 3, 1 directly represent the physical count of each distinct block shape in the expansion.
Extension to PolynomialsGeneralizes spatial thinking from 2D area expansion (a + b)² = a² + 2ab + b² to three-dimensional Euclidean volumes.
Volume Breakdown of the 8 Sub-Blocks Comprising (a + b)³0991972963948b³ (Small Cube)603ab² (3 Slender Prisms)125a³ (Large Cube)1503a²b (3 Flat Prisms)343Total (a+b)³ AssemblyAlgebraic Component TermTotal Volume Contribution (cm³)

Sample readings. Replace with your own results.

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