RBSE Solutions for Class 7 Maths Chapter 14 Symmetry Ex 14.2

Rajasthan Board RBSE Solutions for Class 7 Maths Chapter 14 Symmetry Ex 14.2 Textbook Exercise Questions and Answers.

RBSE Class 7 Maths Solutions Chapter 14 Symmetry Ex 14.2

Question 1.
Which of the following figures have rotational symmetry of order more than 1 ?

Answer:
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 :

Answer:
(a) Rotational symmetry of order 2.
(b) Rotational symmetry of order 2.
(c) Rotational symmetry of order 3.
(d) Rotational symmetry of order 4.
(e) Rotational symmetry of order 4.
(f) Rotational symmetry of order 5.
(g) Rotational symmetry of order 6.
(h) Rotational symmetry of order 3.

Explanation:
(a)

Mark a point A as shown in figure (i). We see that in a full turn, there are two positions (on rotation through the angles 180° and 360°) when the figure looks exactly the same.
Because of this, it has a rotational symmetry of order 2.

(b)

Mark a point P as shown in figure (i). We see that in a full turn, there are two positions (on rotation through the angles 180° and 360°) when the figure looks exactly the same.
Because of this, it has a rotational symmetry of order 2.

(c)

Mark a point A as shown in figure (i). We see that in a full turn, there are three positions (on rotation through the angles 120°. 240° and 360°) when the figure looks exactly the same.
Because of this, it has a rotational symmetry of order 3.

(d)

Mark a point A in fig. (i). We see that in a full turn, there are four positions (one rotation through 90°, 180°, 270° and 360°) when the figure looks exactly the same. So, we say that it has a rotational symmetry of order 4.

(e) Similarly, in a full turn, there are four positions (on rotation through angles 90°, 180°, 270° and 360°) when the figure looks exactly the same.
∴ It has a rotational symmetry of order 4.

(f) The figure is a regular pentagon. In a full turn, there are five positions (ori rotation through the angles 72°, 144°, 216°, 288° and 360°) when the figure looks exactly the same.
∴ It has a rotational symmetry of order 5.

(g) In a full turn, there are six positions (on rotation through the angles 60°, 120°, 180°, 240°, 300° and 360°) when the figure looks exactly the same.
∴ It has a rotational symmetry of order 6.

(h) Order = 3 (120°, 240° and 360°).