In a triangle, if two angles measure 60° and 70°, what is the measure of the third angle?

In a triangle, if two angles measure 60° and 70°, what is the measure of the third angle?

• A. 60
• B. 70
• C. 90
• D. 50

Answer: (D)

In any triangle, the interior angles always sum to 180 degrees. So the third angle is 180 degrees minus the sum of the two given angles. Adding 60° and 70° gives 130°, and 180° − 130° equals 50°. Therefore the third angle measures 50 degrees, completing a set of angles that add to 180°.

In any triangle, the interior angles always sum to 180 degrees. So the third angle is 180 degrees minus the sum of the two given angles. Adding 60° and 70° gives 130°, and 180° − 130° equals 50°. Therefore the third angle measures 50 degrees, completing a set of angles that add to 180°.