Question

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

Answer 1

The formula for sum of interior angles of a n sided polygon is

Sum of interior angles = (n-2)×180°

It is given that sum of interior angles of a polygon = 1980°

Let the number of sides = n

Thus (n-2)×180 = 1980

Or n-2 = 1980/180

Or n-2 = 11

Or n = 11+2 = 13

He.ce, the polygon has 13 sides.

Answer 2

TO Find The Sum Of Interior Angle

we Use The Formula = (n -2 ) *180

As The Given interior Angle = 1980

so , (n -2) *180 = 1980

( n - 2) = 1980 /180

n - 2 = 11

Hence Polygon = n = 11 +2 = 13

So The Side Of Polygon = 13