NCERT - Mathematics

Book: NCERT - Mathematics

Chapter: 3. Understanding Quadrilaterals

Subject: Maths - Class 8th

Q. No. 4 of Exercises 3.1

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4

Examine the table. (Each figure is divided into triangles and the sum of the angles deduced from that)


What can you say about the angle sum of a convex polygon with number of sides?


A. 7


B. 8


C. 10


D. n

From the table, it can be concluded that the angle sum of a convex polygon of n sides

is (n −2) × 180°.


Hence, the angle sum of the convex polygons having number of sides as above will be as follows:


A. Given number of sides =7


Therefore,


(7 − 2) × 180o = 900°


B. Given number of sides = 8


Therefore,


(8 − 2) × 180o = 1080°


C. Given number of sides = 10


Therefore,


(10 − 2) × 180o = 1440°


D. Given number of sides =n


Therefore,


(n − 2) × 180o


5

Chapter Exercises

Exercises 3.1
Exercises 3.2
Exercises 3.3
Exercises 3.4

More Exercise Questions

1

Given here are some figures

(1) (2)


(3) (4)


(5) (6)


(7) (8)


Classify each of them on the basis of the following:


A. Simple curve


B. Simple closed curve


C. Polygon


D. Convex polygon


E. Concave polygon
2

How many diagonals does each of the following have?

A. A convex quadrilateral


B. A regular hexagon


C. A triangle
3

What is the sum of the measures of the angles of a convex quadrilateral? Will this property hold if the quadrilateral is not convex? (Make a non-convex quadrilateral and try!)
4

Examine the table. (Each figure is divided into triangles and the sum of the angles deduced from that)


What can you say about the angle sum of a convex polygon with number of sides?


A. 7


B. 8


C. 10


D. n
5

What is a regular polygon?

State the name of a regular polygon of


(i) 3 sides


(ii) 4 sides


(iii) 6 sides
6

Find the angle measure x in the following figures

A.


B.


C.


D.

7

A. Find x + y + z



B. Find x + y + z + w