Page 231 - Start Up Mathematics_7
P. 231
solve Mentally
True or False
1. The angle of rotation of a figure is obtained by dividing 360° by order of rotational symmetry.
2. A figure not having rotational symmetry can have 3 lines of symmetry.
3. A rhombus is also a parallelogram hence it does not have line symmetry.
4. If a figure is folded in two equal parts such that the two folds overlap each other exactly, then
the figure is symmetrical and the crease so formed is the line of symmetry.
5. A capital letter and its corresponding small letter have equal number of lines of symmetry.
6. If a figure possesses rotational symmetry, then it should look exactly the same at least once
upto a rotation of 180°.
l
7. In the adjoining figure, l is the vertical line of reflection symmetry.
8. In a regular pentagon, the perpendicular bisectors of the sides are the only lines of symmetry.
Fill in the Blanks
1. While opening the cap of a bottle, the direction of rotation is _____________.
2. ____________ is moving a figure parallel to itself along a line.
3. If after a rotation of 45° about a point the figure looks exactly the same, then the order of
rotation is ________________.
4. Number of lines of symmetry of an isosceles right-angled triangle is _________.
5. Angle of rotation of a figure which fits on to itself 3 times in a complete revolution is _______.
6. Angle of rotation of a regular hexagon is ____________.
7. A figure is said to have ____________ symmetry if it has 180° rotational symmetry.
8. A figure has ____________ symmetry if it is its own image under a reflection.
Answer in One Word or a Line
1. How many lines of symmetry does a square have?
2. What is the order of rotational symmetry of a square?
3. Does a parallelogram have line symmetry or rotational symmetry or both?
4. How many lines of symmetry does a rhombus have? What are these?
5. What is centre of rotation?
6. What is angle of rotation of a rectangle?
7. Can we have an angle of rotation of measure 37°?
let’s evaluate
1. Give example of four objects around you which have line symmetry.
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