DAV Board Class 3 Mathematics (Primary Mathematics) | 100% Authentic Textbook Solutions
DAV Class 3 Maths Unit 12 Solutions Geometry
Get complete, step-by-step textbook solutions for DAV Class 3 Primary Mathematics Unit 12: Geometry. This comprehensive guide covers all unit worksheets: Point, Line, Line Segment, Ray, types of lines (horizontal, vertical, slanting, curved), 2D plane figures (Square, Rectangle, Triangle, Circle), and 3D solid figures (Cube, Cuboid, Sphere, Cylinder, Cone) with their exact faces, edges, and vertices strictly adhering to the DAV CMC curriculum.
| Class | Subject | Textbook | Unit Number & Title | Key Mathematical Concepts |
|---|---|---|---|---|
| Class 3 | Mathematics | Primary Mathematics | Unit 12: Geometry | Point, line, ray, line segment, 2D plane shapes, 3D solid shapes (faces, edges, vertices) |
Worksheet 1: Point, Line, Line Segment, and Ray
Comparison Table of Fundamental Geometrical Terms:
| Geometrical Concept | Symbol / Representation | Number of Endpoints | Has Definite Length? | Key Defining Feature |
|---|---|---|---|---|
| Point | • P | 0 | No length, breadth, or thickness | Marks an exact location in space |
| Line | $overleftrightarrow{AB}$ | 0 (none) | No (extends endlessly both sides) | Has arrows on both ends |
| Line Segment | $overline{AB}$ | 2 fixed endpoints | Yes (can be measured with a ruler) | A definite part of a line |
| Ray | $overrightarrow{AB}$ | 1 initial starting point | No (extends endlessly in one direction) | Like a beam of light from the sun or a torch |
Worksheet 2: Plane (2D) Shapes and Properties
| Plane Shape (2D) | Number of Sides | Number of Corners (Vertices) | Essential Geometric Properties |
|---|---|---|---|
| Square | 4 straight sides | 4 corners | All 4 sides are of strictly equal length. |
| Rectangle | 4 straight sides | 4 corners | Opposite sides are equal in length. |
| Triangle | 3 straight sides | 3 corners | Enclosed by three line segments. |
| Circle | 0 straight sides (1 curved boundary) | 0 corners | Round shape with every point equidistant from the center. |
Worksheet 3: Solid (3D) Shapes (Faces, Edges, and Vertices)
Key Definitions:
• Face: The surface of a solid shape (can be flat or curved).
• Edge: The line segment where two faces meet.
• Vertex (Corner): The point where three or more edges meet.
| Solid Shape (3D) | Faces (Flat / Curved) | Edges (Straight / Curved) | Vertices (Corners) | Real-Life Examples |
|---|---|---|---|---|
| Cube | 6 flat square faces | 12 straight edges | 8 vertices | Playing die, sugar cube, Rubik’s cube |
| Cuboid | 6 flat rectangular faces | 12 straight edges | 8 vertices | Maths textbook, pencil box, brick, shoe box |
| Sphere | 1 curved face (0 flat faces) | 0 edges | 0 vertices | Football, globe, orange, marble |
| Cylinder | 2 flat circular faces + 1 curved face | 2 curved edges | 0 vertices | Drinking glass, cold drink can, candle, pipe |
| Cone | 1 flat circular face + 1 curved face | 1 curved edge | 1 vertex (apex) | Birthday party cap, ice-cream cone, traffic cone |
Brain Teasers (DAV CMC Geometry Questions)
Q1. Fill in the blanks with correct mathematical terms:
- (a) A line segment has two endpoints.
- (b) A ray has only one endpoint.
- (c) A cylinder has two flat circular faces and one curved face.
- (d) A brick has the shape of a cuboid.
- (e) A circle has no corners.
- (f) All the faces of a cube are squares.
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