Page 193 - Math Skill - 5

Pattern, Net and Symmetry 191

Rotation
In rotational symmetry, the image is rotated about a point. The point is known as centre of
rotation. This point can be on the figure or any other point.

Rotational Symmetry: When an object can be rotated about a point to
get the same look, it is said to have rotational symmetry. The number
of times it matches itself is called the order of symmetry. You will
understand it further through the given illustrations. O
This figure has been
rotated about point O.
Similarly, a flower can be rotated to match itself a number of times. This
flower can be rotated to match itself 5 times. Hence it has rotational
symmetry of order 5.

A ceiling fan has a rotational symmetry of order 3.

Symmetry in 3D Shapes

Can solids be symmetrical? Let’s find out. Take a ball and cut it into two equal halves. Is it
possible?

The answer is yes. It can be done as shown above. You will get exactly two equal halves. So,
they are symmetrical.
This is called plane of symmetry.

Exercise 15.3

1. Encircle the shapes that have been rotated.

(a) (b) (c)