SSC CGL 2025 PYQ — Question 68

The correct answer is option 1 i.e. 9.

Let the sides of the polygon = n

Interior angle $= \frac{(n-2) \times 180}{n}$

Exterior angle = 360/n

Interior angle − Exterior angle = 100°

⇒ $\frac{180(n-2)}{n} - \frac{360}{n} = 100$

⇒ $\frac{180n - 360 - 360}{n} = 100$

⇒ (180n - 720)/n = 100

⇒ 180n - 720 = 100n

⇒ 80n = 720

⇒ n = 9