The sum of interior angles of a triangle is 180 degrees. If a triangle has angles 50° and 60°, what is the third angle?

The sum of interior angles of a triangle is 180 degrees. If a triangle has angles 50° and 60°, what is the third angle?

• A. 60°
• B. 90°
• C. 70°
• D. 50°

Answer: (C)

In a triangle, all interior angles add up to 180 degrees. With two angles measuring 50° and 60°, the remaining angle must bring the total to 180°. Subtract their sum from 180: 180 − (50 + 60) = 180 − 110 = 70. So the third angle is 70°. This works because 50° + 60° + 70° = 180°. If the third angle were 60°, the total would be 170°; if it were 90°, the total would be 200°; if it were 50°, the total would be 160°. Only 70° satisfies the 180° total.

In a triangle, all interior angles add up to 180 degrees. With two angles measuring 50° and 60°, the remaining angle must bring the total to 180°. Subtract their sum from 180: 180 − (50 + 60) = 180 − 110 = 70. So the third angle is 70°. This works because 50° + 60° + 70° = 180°. If the third angle were 60°, the total would be 170°; if it were 90°, the total would be 200°; if it were 50°, the total would be 160°. Only 70° satisfies the 180° total.