In a triangle with angles of 30° and 60°, what is the measure of the third angle?

In a triangle with angles of 30° and 60°, what is the measure of the third angle?

• A. 60°
• B. 90°
• C. 120°
• D. 30°

Answer: (B)

In any triangle, the sum of the interior angles always equals 180 degrees. Given the triangle has two angles measuring 30 degrees and 60 degrees, we can find the third angle by subtracting the sum of the known angles from 180 degrees. First, calculate the sum of the known angles: 30 degrees + 60 degrees = 90 degrees. Now, subtract this sum from 180 degrees to find the measure of the third angle: 180 degrees - 90 degrees = 90 degrees. Thus, the measure of the third angle in this triangle is 90 degrees, confirming that this option correctly adheres to the fundamental property of triangles regarding angle sums.

In any triangle, the sum of the interior angles always equals 180 degrees. Given the triangle has two angles measuring 30 degrees and 60 degrees, we can find the third angle by subtracting the sum of the known angles from 180 degrees.

First, calculate the sum of the known angles:

30 degrees + 60 degrees = 90 degrees.

Now, subtract this sum from 180 degrees to find the measure of the third angle:

180 degrees - 90 degrees = 90 degrees.

Thus, the measure of the third angle in this triangle is 90 degrees, confirming that this option correctly adheres to the fundamental property of triangles regarding angle sums.