Page 146 - Revised Maths Wisdom Class - 6
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144 MATHS
Rotational Symmetry
The rotational symmetry of a shape describes how, when an object is rotated on its own axis, the shape of the
object remains the same.
Position afterPosition afterPosition afterPosition afterPosition after
Position afterPosition afterPosition afterPosition afterPosition after
Position afterPosition afterPosition afterPosition afterPosition after Position afterPosition afterPosition afterPosition afterPosition after
270° turn270° turn270° turn
360° turn360° turn360° turn360° turn270° turn
180° turn180° turn 180° turn180° turn
90° turn 90° turn 90° turn90° turn90° turn 180° turn 270° turn 360° turn
O O O O O
O O O O O O O O O O
O OO OO OO O O O
Rotational symmetry implies that an object rotates around a fixed point. This fixed location is known as the center
of rotation.
An angle through which a figure can be rotated to look exactly the same is called an angle of rotational symmetry.
A shape has rotational symmetry when it can be rotated and it still looks the same. The order of rotational
symmetry of a shape is the number of times it can be rotated around a full circle and still look the same.
360°
Orderofsymmetry=
Angleofrotation
For the shape of square, the angles of symmetry are 90° (quarter turn), 180° (half turn), 270° (three-quarter turn)
and 360° (full turn). So after every 90°, the shape of square repeats then the angle of symmetry of square is 90°.
Thus, we see that the shape of square has 4 order of symmetry.
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REVIEW TIMEEVIEW TIME
COMPETENCY BASED QUESTIONS
A Oral QuizOral Quiz
1. What is a line of symmetry? 7. A regular hexagon has six lines of symmetry. Is it
2. How many lines of symmetry are there in letter true or false?
“O”? 8. Name a letter from Hindi alphabets which is
3. How many lines of symmetry does an isosceles symmetrical?
triangle has? 9. Name a digit which is symmetrical. How many lines
4. Which type of trapezium has a vertical symmetry? of symmetry it has?
5. Which letter of English alphabets has exactly two 10. How many lines of symmetry a regular octagon
lines of symmetry? has?
6. Is parallelogram symmetrical?
