Question

How many sides has a polygon the sum of whose interior angles is 1980°
a)10
b)13
c)11
d)None of these

Answer 1

the polygon has 13 sides

Explanation:

Sum of interior angles S=(n−2)×180∘,
where n is the number of sides of the polygon.

Given S=1980∘
⇒1980=(n−2)×180
⇒n−2=1980180=11
⇒n=11+2=13

Hence, the polygon has 13 sides.

Answer 2

(n-2)×180 =1980
n-2=1980/180
n-2=11
n=13


the polygon has 13 sides...
I