Rs Aggarwal 2017 Solutions for Class 7 Math Chapter 18 Reflection And Rotational Symmetry are provided here with simple step-by-step explanations. These solutions for Reflection And Rotational Symmetry are extremely popular among Class 7 students for Math Reflection And Rotational Symmetry Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Rs Aggarwal 2017 Book of Class 7 Math Chapter 18 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Rs Aggarwal 2017 Solutions. All Rs Aggarwal 2017 Solutions for class Class 7 Math are prepared by experts and are 100% accurate.

Page No 216:

Answer:

(a) no line of symmetry

Page No 216:

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(c) a line joining the midpoints of its opposite sides

Page No 216:

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(d) four lines of symmetry

A square is symmetrical about both of its diagonals and both lines joining the midpoints of its opposite sides.

Page No 216:

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(b) each of its diagonal

Page No 216:

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(d) an unlimited number of lines of symmetry

A circle is symmetrical about all its diameters and a circle has unlimited number of diameters.
Therefore, a circle has unlimited number of lines of symmetry.

Page No 216:

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(a) AD

This triangle is symmetrical only about AD.
Any isosceles triangle is symmetrical about its one altitude, which is drawn from the vertex between the two equal sides to the unequal side of the triangle.

Page No 216:

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(a) the diagonal AC


Since the part ABC is symmetrical to the part ADC, AC divides the figure into two equal parts.



Page No 217:

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(c) two lines of symmetry

The letter O of the English alphabetic system is symmetrical about its horizontal and vertical line.

Page No 217:

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(a) no line of symmetry

Page No 217:

Answer:

Lines of symmetry are shown by the dotted lines.
(i)

(ii)


(iii)


(iv)

Page No 217:

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(i) True

(ii) True

(iii) True


(iv) False

A rhombus is symmetrical about both of its diagonals.
So, a rhombus has two lines of symmetry.

(v) True

A square is symmetrical about both of its diagonals and both the lines joining the midpoints of its opposite sides.
So, a square has four lines of symmetry.

(vi) True

A rectangle is symmetrical about both the lines joining the midpoints of its opposite sides.
So, a rectangle has two lines of symmetry.

(vii) True

Each one of the letters, H, I, O and X, of the English alphabetic system is symmetrical about its horizontal and vertical line, in the middle of the letters.
So, all these letters have two lines of symmetry.



Page No 219:

Answer:

(i) An equilateral triangle has 3 lines of symmetry.


(ii) The number of positions a figure can be rotated to, without bringing in any changes to the way it looked originally, is called its order of rotational symmetry.
So, the order of rotational symmetry of an equilateral triangle is 3.

 

Page No 219:

Answer:

If we rotate a rectangle by either 180° or 360°, it will look the same as it looked originally, i.e. it will be symmetrical.

Page No 219:

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If we rotate the square either by 90o, 180o, 270o or by 360o, the square looks exactly the same.
Therefore, the order of rotational symmetry of a square is 4.

Page No 219:

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(i) A rhombus has 2 lines of symmetry.

(ii) When we rotate the rhombus either by 180° or by 360°, it looks the same.
Therefore, the rotational symmetry of a rhombus is 2.

Page No 219:

Answer:

H, O and X are the three letters that have 2 lines of symmetry and their order of rotational symmetry is 2.

Page No 219:

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The line of symmetry of an isosceles triangle is the angle bisector of its vertical angle, which is in-between the equal sides. However, it does not have any rotational symmetry.

Page No 219:

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No, every trapezium does not have a line of symmetry.
Only an isosceles trapezium has a line of symmetry.

Page No 219:

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The perpendicular bisector of the diameter of a circle is its line of symmetry.
No, a semicircle does not have any rotational symmetry as it fits itself only once during a complete rotation.

Page No 219:

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A scalene triangle neither has a line of symmetry nor a rotational symmetry.



Page No 220:

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(i) The line of symmetry of the given figure is 1.
(ii) The order of rotational symmetry of the given figure is 0.

Page No 220:

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(i) The given figure has 2 lines of symmetry.

(ii) The order of rotational symmetry of the given figure is 2.

Page No 220:

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The example of a letter of the English alphabetic system which has (i) no line of symmetry and (ii) rotational symmetry of order 2 is N.



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