Angles and Angle Measurement — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. Two angles form a straight angle. One measures 47°. What is the other?
A) 43°
B) 53°
C) 133°
D) 143°
180 − 47 = 133°.
2. Angle X and a 34° angle are complementary. What is angle X?
A) 46°
B) 56°
C) 66°
D) 146°
90 − 34 = 56°.
3. Three angles of a quadrilateral are 90°, 90°, and 115°. What is the fourth angle?
A) 55°
B) 65°
C) 75°
D) 85°
Quadrilateral angles sum to 360°: 360 − 90 − 90 − 115 = 65°.
4. Which angle is acute?
A) 91°
B) 89°
C) 180°
D) 90°
89° is less than 90°, making it an acute angle.
Part B: Fill in the Blank
Write the correct answer on each line.
1. Two supplementary angles add up to 180 degrees.
Supplementary angles always sum to 180°.
2. If a triangle has angles of 60° and 80°, the third angle is 40 degrees.
Triangle angles sum to 180°: 180 − 60 − 80 = 40°.
3. The complement of a 27° angle is 63 degrees.
90 − 27 = 63°.
4. An angle of 90° minus 15° minus 25° equals 50 degrees.
90 − 15 − 25 = 50°.
5. A straight angle split into three equal parts gives angles of 60 degrees each.
180 ÷ 3 = 60°.