Question

How many sides has a polygon the sum of whose interior angles is 1980°

Answer 1

(n-2)*180/n=1980
N-2/n=1980/180
N-2/n=11
N=11+2
N=13.
No. of sides=13

Answer 2

Let nos. Of side be x
Sun of interior angle 180(x-2)

1980=180(x-2)
1980/180=x-2
11=x-2
11+2=x
13=x


Hence numbers of side is 13