## Geometry: Common Core (15th Edition)

$m$ of the interior angles in a $40$-gon = $6840^{\circ}$
According to the Polygon Angle-Sum Theorem, the sum of all the measures of the interior angles of a polygon is $(n - 2)180$, where $n$ is the number of sides of the polygon. We have a polygon that has $40$ sides. $m$ of the interior angles in a $40$-gon = $(40 - 2)180$ Evaluate what is in parentheses first, according to order of operations: $m$ of the interior angles in a $40$-gon = $(38)180$ Multiply to solve: $m$ of the interior angles in a $40$-gon = $6840^{\circ}$