College Math Placement Practice Test 2025 - Free College Math Questions and Study Guide

In any triangle, the sum of all three interior angles always equals 180°. In this case, you have two angles given: 30° and 60°. To find the measure of the third angle, you can use the equation that represents the sum of the angles in a triangle:

30° + 60° + x = 180°

Here, x represents the measure of the third angle. First, you can sum the known angles:

30° + 60° = 90°

Now, substitute this value back into the equation:

90° + x = 180°

To solve for x, subtract 90° from both sides:

x = 180° - 90°

x = 90°

Thus, the measure of the third angle is 90°. This makes the triangle a right triangle, since one of the angles measures 90°. The presence of a right angle is significant in geometric contexts, as it implies various properties and theorems applicable to right triangles. It's worth noting that the other options provided do not satisfy the requirement that all angles in a triangle must sum to 180°, which is why only the measure of 90° is correct in this scenario.