if the sum of the exterior angles of a polygon is one-fifth of the sum of the interior angles of the polygon, how many sides does the polygon have?

As the measure of the exterior angles of a regular polygon are 15 times the measure of its interior angles, each exterior angle of the regular polygon too will be 15 times the measure of its interior angle. we have 360∘30∘=12 exterior or interior angles i.e. Polygon has 12 sides - it is dodecagon