The difference between an interior angle and an exterior angle of a regular polygon is 140°. Find the number of sides of the polygon.​

Correct option is C

Given:

The difference between an interior angle and an exterior angle of a regular polygon is 140°

Formula Used:

Interior angle + Exterior angle = 180°

Exterior angle of a regular polygon = $$\frac{360}{n}$$​​

Solution: 

​Let exterior angle = x, then interior angle = 180 - x

So,

(180 - x) - x = 140

180 - 2x = 140

2x = 40

x = 20

Now,

$$\frac{360}{n}$$​ = 20

n = $$\frac{360}{20}$$​ = 18 sides