Question

The measure of an angle whose supplement is equal to itself is

• A. ${65}^{\circ }$
• B. ${45}^{\circ }$
• C. ${180}^{\circ }$
• D. ${90}^{\circ }$

Answer 1

The correct option is D ${90}^{\circ }$

Let the measure of the angle be $x^{\circ }$.
Then,
$x^{\circ }+x^{\circ }={180}^{\circ }\left[\text{since they are supplementary}\right]\Rightarrow 2x^{\circ }={180}^{\circ }\Rightarrow x^{\circ }={90}^{\circ }$