we know that
The exterior angle measures of a polygon must add up to 360°,
therefore
360°/72°=5 exterior angles
so
5 exterior angles, would mean 5 interior angles and therefore 5 sides to the polygon
The exterior angle and the interior angle of any polygon are supplementary and must add up to 180°.
exterior angle+interior angle=180°
interior angle=180°-exterior angle
interior angle=180°−72°-------> 108°
Each interior angle is 108°
The sum of the interior angles would be
5*108°=540°
the answer is
540°