What is a supplementary angle?

What is a supplementary angle?

• A. Add up to 90 degrees.
• B. Sum to 360 degrees.
• C. Add up to 180 degrees.
• D. Add up to 270 degrees.

Answer: (C)

Supplementary angles are two angles whose measures add up to 180 degrees. This comes from the idea of a straight angle, which measures 180 degrees. When two angles share a vertex and their non‑common sides form a straight line, their measures total 180. For example, if one angle is 60 degrees, the other is 120 degrees. The option describing a sum of 180 degrees is the correct description. The other possibilities—summing to 90 degrees (complementary angles), 360 degrees (a full circle), or 270 degrees (three quarters of a circle)—do not describe supplementary angles.

Supplementary angles are two angles whose measures add up to 180 degrees. This comes from the idea of a straight angle, which measures 180 degrees. When two angles share a vertex and their non‑common sides form a straight line, their measures total 180. For example, if one angle is 60 degrees, the other is 120 degrees. The option describing a sum of 180 degrees is the correct description. The other possibilities—summing to 90 degrees (complementary angles), 360 degrees (a full circle), or 270 degrees (three quarters of a circle)—do not describe supplementary angles.