Question

Two angles in a triangle have measures of 25° and 55°.

What is the measure of the third angle?

A.
30°
B.
100°
C.
135°
D.
80°

Answer 1

In a triangle, the sum of the measures of the angles is always 180°.

Given the two angles:

- First angle = 25°
- Second angle = 55°

To find the third angle, you can use the formula:

\[
\text{Third angle} = 180° - (\text{First angle} + \text{Second angle})
\]

Substituting the known values:

\[
\text{Third angle} = 180° - (25° + 55°)
\]
\[
\text{Third angle} = 180° - 80°
\]
\[
\text{Third angle} = 100°
\]

Therefore, the measure of the third angle is **100°**.

The correct answer is **B. 100°**.