Answer:
option B
Step-by-step explanation:
Sum of interior angles of a polygon with n sides:
[tex]= (n - 2 )\times 180[/tex]
[tex]Therefore, Each \ interior \ angle = (\frac{n - 2}{n} )\times 180[/tex]
[tex]Sum \ of \ one \ of \ the \ interior \ angle \ with \ its \ exterior \ angle \ is \ 180^\circ[/tex]
[tex][ \ because \ straight \ line \ angle = 180^\circ \ ][/tex]
That is ,
[tex]Exterior \ angle + Interior \ angle = 180^\circ\\\\40^ \circ + (\frac{n-2}{n}) \times 180 = 180^\circ\\\\40 n + 180n - 360 = 180n\\\\40n = 180n - 180n + 360 \\\\40n = 360 \\\\n = 9[/tex]
OR
Sum of exterior angles of a regular polygon = 360
Given 1 exterior angle of the regular polygon is 40
Therefore ,
[tex]n \times 40 = 360\\\\n = \frac{360}{40} \\\\n = 9[/tex]