If an angle is equal to one third of its supplement, its measure is equal to

Let the required angle be x and the supplement of x is y.

As we know if two angles are supplement of each other, then sum of those two angles is 180°.

⇒ x + y = 180

⇒ y = 180 – x

Now, according to question;

Required angle is equal to one third of its supplement;

i.e.

⇒ y = 3x

Now putting the value of y in this equation,

⇒ 180 – x = 3x

⇒

⇒

⇒

Hence, required angle is 45°.

Hence, correct option is (c).