Geometry · Angles

Angles & Triangles

Angle types, angle relationships, and the triangle angle sum.

Score: 0 / 10

1. The interior angles of a triangle add up to how many degrees?

2. A triangle has angles of 50° and 60°. What is the third angle?

3. What type of triangle has all three sides equal?

4. What type of angle measures exactly 90°?

5. An angle that measures more than 90° but less than 180° is called:

6. A triangle has a right angle (90°) and one other angle of 35°. What is the third angle?

7. Two angles that add up to 180° are called:

8. Two angles that add up to 90° are called:

9. A triangle with exactly two equal sides is called:

10. An angle less than 90° is called:

Answer key — Angles & Triangles

B — 180. Every triangle’s interior angles sum to 180°.
B — 70. The angles sum to 180°: 180 − 50 − 60 = 70°.
C — Equilateral. An equilateral triangle has three equal sides and three equal 60° angles.
B — Right. A 90° angle is a right angle.
C — Obtuse. Between 90° and 180° is obtuse.
B — 55. 180 − 90 − 35 = 55°.
B — Supplementary. Angles that sum to 180° are supplementary.
A — Complementary. Angles that sum to 90° are complementary.
C — Isosceles. An isosceles triangle has exactly two equal sides.
A — Acute. Less than 90° is acute.

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