NCERT Solutions for Class 7 Maths Chapter 14 Symmetry Ex 14.2

Class 7 Maths NCERT Solutions Chapter 14 Symmetry Ex 14.2

Question 1.
Which of the following figures have rotational symmetry of order more than 1:
(a)

(b)

(c)

(d)

(e)

(f)

Solution:
Figures (a), (b), (d), (e), and (f) have rotational symmetry of order more than 1.

Question 2.
Give the order of rotational symmetry for each figure :
(a)

Solution:
Let us mark a point A on each figure and also indicate the angle through which the figure is to be rotated as under :

(b)

Solution:
Let us mark a point A on each figure and also indicate the angle through which the figure is to be rotated as under :

(c)

Solution:
Let us mark a point A on each figure and also indicate the angle through which the figure is to be rotated as under :

(d)

Solution:
Let us mark a point A on each figure and also indicate the angle through which the figure is to be rotated as under :

(e)

Solution:
Let us mark a point A on each figure and also indicate the angle through which the figure is to be rotated as under :

(f)

Solution:
Let us mark a point A on each figure and also indicate the angle through which the figure is to be rotated as under :

(g)

Solution:
Let us mark a point A on each figure and also indicate the angle through which the figure is to be rotated as under :

(h)

Solution:
Let us mark a point A on each figure and also indicate the angle through which the figure is to be rotated as under :

Now to find the rotational symmetry, we proceed as under :

In figure (a): it requires two rotations, each through an angle of 180°, about the marked point (x) to come back to its original position. So, its rotational symmetry is of order 2.

In figure (b): It requires two rotations, each through an angle of 180°, about the marked point (x) to come back to its original position. So, its rotational symmetry is of order 2.

In figure (c): The triangle requires three rotations, each through an angle of 120° about the marked point to come back to its original position. So, it has rotational symmetry of order 3.

In figure (d): The figure requires four rotations, each through an angle of 90°, about the marked point (x) to come back to its original position. So, its rotational symmetry is of order 4.

n figure (e): The figure requires four rotations, each through an angle of 90°, about the marked point (x) to come back to its original position. So, its rotational symmetry is of order 4.

In figure (f): The regular pentagon requires five rotations, each through an angle of 72°, about the marked point to come back to its original position. So, it has rotational symmetry of order 5.

In figure (g): The figure requires six rotations, each through an angle of 60°, about the marked point to come back to its original position. So, it has rotational symmetry of order 6.

In figure (h): The figure requires three rotations each through an angle of 120°, about the marked point to come back to its original position. So, it has rotational symmetry of order 3.