CBSE NCERT Solutions for Class 8 Chapter 3

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CBSE NCERT Solutions for Class 8 Maths Chapter 3:

Question-1:

Find the measure of each exterior angle of a regular polygon of:
(a) 9 sides (b) 15 sides

Solution:

(i) Sum of angles of a regular polygon = (n-2) x 1800
=(9-2)x1800
=7x1800
= 12600
Each interior angle = sum of interior angle /number of sides = 12600/9 = 1400
Each exterior angle = 1800– 1400= 400
(ii) Sum of exterior angles of a regular polygon = 3600
Each Exterior angle of a regular polygon has the same measure.
Thus , measure of each exterior angle angle of a regular polygon of 15sides
= 360o/15 = 24o

Question-2:

How many sides does a regular polygon have, if the measure of an exterior angle is 240?

Solution:

Let number of sides be n.
Sum of exterior angles of a regular polygon = 3600
Number of sides = sum of interior angle /number of sides = 3600/24 = 15
Hence, the regular polygon has 15 sides.

Question-3:

How many sides does a regular polygon have if each of its interior angle as 1650?

Solution:

Let number of sides be n.
Exterior angle = 1800– 1650= 150
Sum of exterior angles of a regular polygon = 3600
Number of sides = sum of interior angle /number of sides = 3600/15 = 25
Hence, the regular polygon has 24 sides.

Question-4:

(a) How many sides does a regular polygon have if each of its interior angle as 220?
(b) Can it be an interior angle of a regular polygon? Why?

Solution:

(a) No. ( Since 22 is not a divisor of 3600)
(b) No, ( Because each exterior angle is 1800– 220= 1580 , which is not a divisor of 360