Gujarat BoardĀ GSEB Textbook Solutions Class 7 Maths Chapter 14 Symmetry Ex 14.2 Textbook Questions and Answers.
Gujarat Board Textbook Solutions Class 7 Maths Chapter 14 Symmetry Ex 14.2
Question 1.
Which of the following figures have rotational symmetry of order more than 1:
Solution:
The 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:
Solution:
(a)
Let us mark a point P as shown in the figure (i). It requires two rotations, each through 180° about the point (X) to come back to its original position.
ā“ It has a rotational symmetry of order 2.
(b)
Mark a point P as shown is figure (i). It requires two rotations, each through an angle of 180°, about the marked point (X) to come back to its original position.
Thus, it has a rotational symmetry of order 2.
(c)
Mark a point P as shown in figure (i) It requires three rotations, each through an angle of 120°, about the marked point (X) to come back to its original position.
Thus, it has a rotational symmetry of order 2.
(d)
Mark a point P as shown in Fig. (i). It requires four rotations, each through an angle of 90°, about the marked point (X) to come back to its original position.
Thus, it has a rotational symmetry of order 4.
Similarly,
(e) The figure requires four rotations each of 90°, about the marked point (X) to come back to its original position.
ā“ It has a rotational symmetry of order 4.
(f) The figure is a regular pentagon. It requires five rotations, each through an angle of 72°, about the marked point to come back to its original position.
ā“ It has rotational symmetry of order 5.
(g) The given figure requires six rotations, each through an angle of 60°, about the marked point (X) to come back to its original position.
Thus, it has a rotational symmetry of order 6.
(h) The given figure requires three rotations, each through an angle of 120°, about the marked point (X), to come back to its original position.
ā“ Its has a rotational symmetry of order 3.