If a triangle has angles measuring 30° and 60°, what is the measure of the third angle?

• A. 60°
• B. 90°
• C. 30°
• D. 120°

Answer: (B)

To determine the measure of the third angle in a triangle, we utilize the fundamental property that the sum of all interior angles in any triangle is always 180°.

In this particular case, two angles are provided: 30° and 60°. To find the third angle, we first add the two known angles:

30° + 60° = 90°.

Next, we subtract this sum from 180°:

180° - 90° = 90°.

Thus, the measure of the third angle is 90°. This conclusion aligns with our understanding of triangle angle properties, confirming that one angle can be 90° in a right triangle, which is indeed a possibility for the angle measures provided.