NCERT Solutions Class 7 Math Chapter 12 Symmetry Exercise 12.2

NCERT Solutions Class 7 Math Chapter 12 Symmetry Exercise 12.2

TextbookNCERT
Class 7th
Subject Math
Chapter12th
Chapter NameSymmetry
CategoryClass 7th Math Solutions 
Medium English
SourceLast Doubt

NCERT Solutions Class 7 Math Chapter 12 Symmetry Exercise 12.2

Chapter – 12

Symmetry

Exercise 12.2

Question 1.Which of the following figures have rotational symmetry of order more than 1?
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Solution: The figure (a), (b), (d), (e) and (f) have rotational symmetry more than 1.
Question 2.Give the order of rotational symmetry for each figure:
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Solution:
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Let us take a point S on one end of the given figure. Rotating by 180°, S comes at other end and then again rotating by 180°, it comes at its original position.
∴ Order of rotational symmetry = 360∘180∘=2

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Let us take any point S in figure (1). It takes two rotations to come back to its original position.
∴ Order of rotational symmetry = 360∘180∘=2

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Let us mark any vertex of the given figure. It takes three rotations to come back to its original shape.
∴ Order of rotational symmetry = 360∘120∘=3

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Order of rotational symmetry = 360∘90∘=4

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∴ Order of rotational symmetry = 360∘90∘=4

(f) The given figure is a regular pentagon which can take one rotation at an angle of 72°.
∴ Order of rotational symmetry = 360∘72∘=5

(g) The given figure requires six rotations each through an angle of 60°
∴ Order of rotational symmetry = 360∘60∘=6

(h) The given figure requires three rotations, each through an angle of 120°.
∴ Order of rotational symmetry = 360∘120∘=3