# Ex.3.2 Q6 Understanding Quadrilaterals Solution - NCERT Maths Class 8

Go back to  'Ex.3.2'

## Question

(a) What is the minimum interior angle possible for a regular polygon? Why?

(b) What is the maximum exterior angle possible for a regular polygon?

## Text Solution

What is Known?

We know polygons according to the number of sides (or vertices) they have.

What is Unknown?

Minimum interior angle possible for a regular polygon.

Maximum exterior angle possible for a regular polygon.

Reasoning:We know that the sum of measure of interior angle of triangle is  $$={\rm{18}}0^\circ$$

Equilateral triangle is regular polygon having maximum exterior angle because it consists of least number of sides.

Steps:

(a) What is the minimum interior angle possible for a regular polygon? Why?

Consider a regular polygon having the least number of sides (i.e., an equilateral triangle).

We know Sum of all the angles of a triangle $$= {\rm{18}}0^\circ$$

\begin{align}x + x + x{\rm{ }}& = {\rm{ 18}}0^\circ \\{\rm{3}}x &= {\rm{18}}0^\circ \\x &= \frac{{{\rm{18}}0^\circ }}{3}\\x &= {\rm{6}}0^\circ\end{align}Thus, minimum interior angle possible for a regular polygon$$= 60^\circ$$

(b) What is the maximum exterior angle possible for a regular polygon?

We know that the exterior angle and an interior angle will always form a linear pair. Thus exterior angle will be maximum when interior angle is minimum.

Exterior angle

\begin{align}&= {\rm{18}}{0^{\rm{\circ}}} - \,\,{\rm{6}}0^\circ \\&={120^{\rm{\circ}}}.\end{align}

Therefore, maximum exterior angle possible for a regular polygon is $$120^\circ$$

Equilateral triangle is a regular polygon having maximum exterior angle because it consists of least number of sides.

Learn from the best math teachers and top your exams

• Live one on one classroom and doubt clearing
• Practice worksheets in and after class for conceptual clarity
• Personalized curriculum to keep up with school