Algebraic Identity (a + b)³ 3D Dissection Model
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 setWhat is it?3D Acrylic / Wooden mathematical model set for binomial cube: a = 4 cm, b = 2 cm set₹50
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) × 1What is it?- Cube of side a (4 = 64 cm³) × 1₹95
Digital Vernier Caliper for verifying block face dimensions.
Specifications- Resolution
- 0.01 mm
- Accuracy
- ± 0.02 mm
- - Cube of side b (2 = 8 cm³) × 1What is it?- Cube of side b (2 = 8 cm³) × 1₹140
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) × 3What is it?- Cuboids of dimension a × a × b (4 = 32 cm³) × 3₹185
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) × 3What is it?- Cuboids of dimension a × b × b (4 = 16 cm³) × 3₹230
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 cmWhat is it?Display tray with base 6 cm cm₹275
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 / RulerWhat is it?Metric Vernier Caliper / Ruler₹320
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
- 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.
SafetyInspect 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.
SafetyVerify 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.
SafetyGroup 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.
SafetyCheck 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.
SafetyEnsure 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).
SafetyClose 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 Identity | Quantity in Set | Algebraic Dimensions | Volume per Block (cm³) | Total Sub-Volume (cm³) |
|---|---|---|---|---|
| Block A (Large Cube) | 1 block | a × a × a (5 cm × 5 cm × 5 cm) | a³ = 125.0 cm³ | 125.0 cm³ |
| Block B (Square Prism A) | 3 blocks | a × a × b (5 cm × 5 cm × 2 cm) | a²b = 50.0 cm³ | 3 × 50.0 = 150.0 cm³ |
| Block C (Square Prism B) | 3 blocks | a × b × b (5 cm × 2 cm × 2 cm) | ab² = 20.0 cm³ | 3 × 20.0 = 60.0 cm³ |
| Block D (Small Cube) | 1 block | b × b × b (2 cm × 2 cm × 2 cm) | b³ = 8.0 cm³ | 8.0 cm³ |
| Total Composite Cube | 8 blocks total | (a + b)³ = (5 + 2)³ = 7³ cm³ | (a + b)³ = 343.0 cm³ | 125 + 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.
| Observation | What it means |
|---|---|
| Exact Spatial Volume Conservation | Sum 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 Verified | Physical assembly provides an unforgettable three-dimensional tactile proof of (a + b)³ = a³ + 3a²b + 3ab² + b³. |
| Geometric Significance of Coefficients | The binomial coefficients 1, 3, 3, 1 directly represent the physical count of each distinct block shape in the expansion. |
| Extension to Polynomials | Generalizes spatial thinking from 2D area expansion (a + b)² = a² + 2ab + b² to three-dimensional Euclidean volumes. |
Sample readings. Replace with your own results.