Page 212 - ICSE Math 7

19 Visualizing Solid Shapes

Key Concepts

• Polyhedrons • Visualizing Solid Objects
• Nets of 3D Shapes • Mapping the Space Around Through Visual
• Drawing Solids on a Flat Surface Estimation

In our day-to-day life, we see several objects around us. On careful observation, we find they may
have different shapes and sizes, but yet they may have a common feature in terms of their dimensions.
We know a line has only 1 dimension, i.e., its length. Figures like currency note, postage stamp,
postcard, etc. are examples of plane figures. They have 2 dimensions, i.e., length and breadth. On the
other hand, objects like book, ice cream cone, ball, drum and tube light are examples of solid shapes
having 3 dimensions, i.e., length, breadth and height.

A line

Postage stamp Book
One-dimensional figure Two-dimensional figure Three-dimensional solid

We write 2D for 2 dimensional figures and 3D for 3 dimensional objects.

Let’s recall some 3D shapes studied in previous classes.

(a) (b) (c) (d)

Cuboid Cube
Cone Cylinder

(e) (f) (g)

Sphere Prism Pyramid
Polyhedrons

The solids which are bounded by polygons as their faces are called polyhedrons. Let’s define some
terms associated with a polyhedron.
Faces: The polygons forming a polyhedron are called its faces.
Edges: The line segments where the faces of a polyhedron meet are called its edges.

Vertices: The corners where the edges of a polyhedron intersect are called its vertices.

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