The measure of an exterior angle in a polygon with n sides is given by:
[tex]a_n=\frac{360}{n}[/tex]So, for n = 20, we have the measure of the exterior angles of the polygon with 20 sides:
[tex]\begin{gathered} a_{20}=\frac{360}{20} \\ a_{20}=18\degree \end{gathered}[/tex]Now, to find the sum of all exterior angles, let's multiply the exterior angles by the number of sides of the polygon:
[tex]\begin{gathered} S_{20}=a_{20}\cdot n \\ S_{20}=18\cdot20 \\ S_{20}=360\degree \end{gathered}[/tex]Therefore the sum is equal to 360°, correct option: B.
(The sum of exterior angles of a polygon with n sides is always equal to 360°)
