Solutions For All Chapters Maths Class 7
Ex 12.3 Class 7 Maths Question 1.
Name any two figures that have both line symmetry and rotational symmetry.
Solution:
English alphabet H and O both have line symmetry and rotational symmetry.
Ex 12.3 Class 7 Maths Question 2.
Draw, wherever possible, a rough sketch of
(i) a triangle with both line and rotational symmetries of order more than 1.
(ii) a triangle with only line symmetry and no rotational symmetry of order more than 1.
(iii) a quadrilateral with a rotational symmetry of order more than 1 but not a line symmetry.
(iv) a quadrilateral with line symmetry but not a rotational symmetry of order more than 1
Solution:
(i) Equilateral triangle has 3 rotational symmetries.
(ii) Not possible.
(iii)
(iv) Not possible.
Ex 12.3 Class 7 Maths Question 3.
If a figure has two or more lines of symmetry, should it have rotational symmetry of order more than 1?
Solution:
Yes. The above figure has two lines of symmetry and also rotational symmetry of order 2.
Ex 12.3 Class 7 Maths Question 4.
Fill in the blanks:
| Shape | Centre of rotation | Order of rotation | Angle of rotation |
| Square | |||
| Rectangle | |||
| Rhombus | |||
| Equilateral triangle | |||
| Regular hexagon | |||
| Circle | |||
| Semicircle |
Solution:
| Shape | Centre of rotation | Order of rotation | Angle of rotation |
| Square | Point of intersection of diagonals | 4 | 90° |
| Rectangle | Point of intersection of diagonals | 4 | 90° |
| Rhombus | Point of intersection of diagonals | 4 | 90° |
| Equilateral triangle | Point of intersection of medians | 3 | 120° |
| Regular hexagon | Point of intersection of diagonals | 6 | 60° |
| Circle | Centre | Infinite | Every angle |
| Semicircle | Centre | 4 | 90° |
Ex 12.3 Class 7 Maths Question 5.
Name the quadrilaterals which have both line and rotational symmetry of order more than 1.
Solution:
Square, rectangles and rhombus are such quadrilateral which have both line and rotational symmetry.
Ex 14.3 Class 7 Maths Question 6.
After rotating by 60° about a centre, a figure looks exactly the same as its original position. At what other angles will this happen for the figure?
Solution:
If a figure is rotated through the angles 120°, 180°, 240°, 300° and 360°, it looks exactly the same.
Ex 12.3 Class 7 Maths Question 7.
Can we have a rotational symmetry of order more than 1 whose angle of rotation is
(i) 45°?
(ii) 17°?
Solution:
(i) Yes
(ii) No
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