Which of the following is/are not the interior angle(s) of a regular polygon? I.108° II. 116° III. 120°
-
A.
I only -
B.
II only -
C.
III only -
D.
I and III only
Correct Answer: Option B
Explanation
Using the formula, ((n – 2) times 180°) to get the sum of the interior angles. Then we can have
((n – 2) times 180° = 108n) … (1)
((n – 2) times 180° = 116n) … (2)
((n – 2) times 180° = 120n) … (3)
Solving the above given equations, where n is not a positive integer then that angle is not the interior for a regular polygon.
(1): (180n – 360 = 108n implies 72n = 360)
(n = 5) (regular pentagon)
(2): (180n – 360 = 116n implies 64n = 360)
(n = 5.625)
(3): (180n – 360 = 120n implies 60n = 360)
(n = 6) (regular hexagon)
Hence, 116° is not an angle of a regular polygon.