NCERT Solutions for Class 7 Maths Chapter 14 Symmetry InText Questions

Class 7 Maths NCERT Solutions Chapter 14 Symmetry InText Questions

Try These (page 272)

Question 1.

(a) Can you now tell the order of the rotational symmetry for an equilateral triangle?
Solution:
In a full turn, there is precisely three-position (on rotation through the angles 120°, 240°, and 360°) when the triangle looks exactly the same. Because of this, we can say that it has rotational symmetry of order 3.

(b) How many positions are there at which the triangle looks exactly the same when rotated about its centre by 120°?
Solution:
There is only one position where the triangle looks exactly the same when rotated about its centre.

Question 2.
Which of the following shapes have rotational symmetry about the marked point?
Solution:
(i)

(ii)

(iii)

(iv)

We know that when a figure which on rotation through an angle, about a point, look the same as the original, is said to have rational symmetry. Figures (i), (ii), (iii) and (iv) have rotational symmetry.

Try These (page 273)

Question 1.
Give the order of the rotational symmetry of the given figures about the point marked x :
(i)

Solution:
The find the order of rotation in respect of

Let us mark the end of the vertical rectangle as A. We find that figure required four rotations through 90° each about the point (x) to get back to the original position.
Thus, this figure has rotational symmetry of order 4.

(ii)

Solution:

Clearly, this figure requires three rotations, each through an angle of 120°, about the marked point (x) to come back to its original position. Therefore, it has rotational symmetry of order 3.

(iii)

Solution:

Clearly, this figure requires four rotations, each through an angle of 90°, about the marked point (x) to come back to its original position. Therefore, it has rotational symmetry of order 4