Class 7 Exam  >  Class 7 Notes  >  Mathematics (Maths) Class 7  >  RD Sharma Solutions: Symmetry (Exercise 18.3)

Symmetry (Exercise 18.3) RD Sharma Solutions | Mathematics (Maths) Class 7 PDF Download

Download, print and study this document offline
Please wait while the PDF view is loading
 Page 1


 
 
 
 
 
 
 
 
        
 
1. Give the order of rotational symmetry for each of the following figures when 
rotated about the marked point (x): 
 
Solution: 
(i) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 4. 
 
(ii) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 3. 
 
Page 2


 
 
 
 
 
 
 
 
        
 
1. Give the order of rotational symmetry for each of the following figures when 
rotated about the marked point (x): 
 
Solution: 
(i) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 4. 
 
(ii) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 3. 
 
 
 
 
 
 
 
 
 
(iii) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 3. 
 
(iv) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 4. 
 
(v) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 2. 
 
(vi) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 4. 
 
(vii) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 5. 
 
(viii) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 6. 
 
(ix) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 3. 
 
2. Name any two figures that have both line symmetry and rotational symmetry. 
 
Solution: 
An equilateral triangle and a square have both lines of symmetry and rotational 
symmetry. 
Page 3


 
 
 
 
 
 
 
 
        
 
1. Give the order of rotational symmetry for each of the following figures when 
rotated about the marked point (x): 
 
Solution: 
(i) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 4. 
 
(ii) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 3. 
 
 
 
 
 
 
 
 
 
(iii) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 3. 
 
(iv) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 4. 
 
(v) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 2. 
 
(vi) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 4. 
 
(vii) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 5. 
 
(viii) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 6. 
 
(ix) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 3. 
 
2. Name any two figures that have both line symmetry and rotational symmetry. 
 
Solution: 
An equilateral triangle and a square have both lines of symmetry and rotational 
symmetry. 
 
 
 
 
 
 
 
 
 
 
3. Give an example of a figure that has a line of symmetry but does not have 
rotational symmetry. 
 
Solution: 
A semicircle and an isosceles triangle have a line of symmetry but do not have rotational 
symmetry. 
 
 
4. Give an example of a geometrical figure which has neither a line of symmetry nor a 
rotational symmetry. 
 
Solution: 
A scalene triangle has neither a line of symmetry nor a rotational symmetry. 
Page 4


 
 
 
 
 
 
 
 
        
 
1. Give the order of rotational symmetry for each of the following figures when 
rotated about the marked point (x): 
 
Solution: 
(i) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 4. 
 
(ii) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 3. 
 
 
 
 
 
 
 
 
 
(iii) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 3. 
 
(iv) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 4. 
 
(v) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 2. 
 
(vi) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 4. 
 
(vii) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 5. 
 
(viii) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 6. 
 
(ix) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 3. 
 
2. Name any two figures that have both line symmetry and rotational symmetry. 
 
Solution: 
An equilateral triangle and a square have both lines of symmetry and rotational 
symmetry. 
 
 
 
 
 
 
 
 
 
 
3. Give an example of a figure that has a line of symmetry but does not have 
rotational symmetry. 
 
Solution: 
A semicircle and an isosceles triangle have a line of symmetry but do not have rotational 
symmetry. 
 
 
4. Give an example of a geometrical figure which has neither a line of symmetry nor a 
rotational symmetry. 
 
Solution: 
A scalene triangle has neither a line of symmetry nor a rotational symmetry. 
 
 
 
 
 
 
 
 
 
 
5. Give an example of a letter of the English alphabet which has 
(i) No line of symmetry 
(ii) Rotational symmetry of order 2. 
 
Solution: 
(i) The letter of the English alphabet which has no line of symmetry is Z. 
 
(ii) The letter of the English alphabet which has rotational symmetry of order 2 is N. 
 
6. What is the line of symmetry of a semi-circle? Does it have rotational symmetry? 
 
Solution: 
A semicircle (half of a circle) has only one line of symmetry. In the figure, there is one 
line of symmetry. The figure is symmetric along the perpendicular bisector I of the 
diameter XY. A semi-circle does not have any rotational symmetry. 
 
 
7. Draw, whenever possible, a rough sketch of 
(i) a triangle with both line and rotational symmetries. 
(ii) a triangle with only line symmetry and no rotational symmetry. 
(iii) a quadrilateral with a rotational symmetry but not a line of symmetry. 
(iv) a quadrilateral with line symmetry but not a rotational symmetry. 
Page 5


 
 
 
 
 
 
 
 
        
 
1. Give the order of rotational symmetry for each of the following figures when 
rotated about the marked point (x): 
 
Solution: 
(i) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 4. 
 
(ii) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 3. 
 
 
 
 
 
 
 
 
 
(iii) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 3. 
 
(iv) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 4. 
 
(v) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 2. 
 
(vi) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 4. 
 
(vii) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 5. 
 
(viii) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 6. 
 
(ix) A figure is said to have rotational symmetry if its fits onto itself more than once 
during a full turn that is rotation through 360
o
 
Therefore the given figure has its rotational symmetry as 3. 
 
2. Name any two figures that have both line symmetry and rotational symmetry. 
 
Solution: 
An equilateral triangle and a square have both lines of symmetry and rotational 
symmetry. 
 
 
 
 
 
 
 
 
 
 
3. Give an example of a figure that has a line of symmetry but does not have 
rotational symmetry. 
 
Solution: 
A semicircle and an isosceles triangle have a line of symmetry but do not have rotational 
symmetry. 
 
 
4. Give an example of a geometrical figure which has neither a line of symmetry nor a 
rotational symmetry. 
 
Solution: 
A scalene triangle has neither a line of symmetry nor a rotational symmetry. 
 
 
 
 
 
 
 
 
 
 
5. Give an example of a letter of the English alphabet which has 
(i) No line of symmetry 
(ii) Rotational symmetry of order 2. 
 
Solution: 
(i) The letter of the English alphabet which has no line of symmetry is Z. 
 
(ii) The letter of the English alphabet which has rotational symmetry of order 2 is N. 
 
6. What is the line of symmetry of a semi-circle? Does it have rotational symmetry? 
 
Solution: 
A semicircle (half of a circle) has only one line of symmetry. In the figure, there is one 
line of symmetry. The figure is symmetric along the perpendicular bisector I of the 
diameter XY. A semi-circle does not have any rotational symmetry. 
 
 
7. Draw, whenever possible, a rough sketch of 
(i) a triangle with both line and rotational symmetries. 
(ii) a triangle with only line symmetry and no rotational symmetry. 
(iii) a quadrilateral with a rotational symmetry but not a line of symmetry. 
(iv) a quadrilateral with line symmetry but not a rotational symmetry. 
 
 
 
 
 
 
 
 
 
Solution: 
(i) An equilateral triangle has 3 lines of symmetry and a rotational symmetry of order 3. 
 
 
(ii) An isosceles triangle has only 1 line of symmetry and no rotational symmetry. 
 
 
(iii) A parallelogram is a quadrilateral which has no line of symmetry but a rotational 
symmetry of order 2. 
 
 
Read More
76 videos|345 docs|39 tests

Top Courses for Class 7

76 videos|345 docs|39 tests
Download as PDF
Explore Courses for Class 7 exam

Top Courses for Class 7

Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev
Related Searches

past year papers

,

MCQs

,

Important questions

,

Exam

,

shortcuts and tricks

,

Extra Questions

,

video lectures

,

Summary

,

Semester Notes

,

mock tests for examination

,

Previous Year Questions with Solutions

,

Sample Paper

,

pdf

,

Free

,

Viva Questions

,

practice quizzes

,

Objective type Questions

,

Symmetry (Exercise 18.3) RD Sharma Solutions | Mathematics (Maths) Class 7

,

ppt

,

study material

,

Symmetry (Exercise 18.3) RD Sharma Solutions | Mathematics (Maths) Class 7

,

Symmetry (Exercise 18.3) RD Sharma Solutions | Mathematics (Maths) Class 7

;