Angles and Measurement — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. Angle A and angle B are complementary. Angle A is 28°. What is angle B?
A) 52°
B) 62°
C) 72°
D) 152°
The correct answer is B) 62°. Angle A and angle B are complementary. Angle A is 28°. What is angle B — the answer is 62°.
2. Two supplementary angles differ by 40°. What are the two angles?
A) 60° and 100°
B) 70° and 110°
C) 80° and 120°
D) 90° and 130°
The correct answer is B) 70° and 110°. Two supplementary angles differ by 40°. What are the two angles — the answer is 70° and 110°.
3. A straight angle is split into three angles: 50°, 65°, and x°. What is x?
A) 55°
B) 60°
C) 65°
D) 75°
The correct answer is C) 65°. A straight angle is split into three angles: 50°, 65°, and x°. What is x — the answer is 65°.
4. Which pair of angles is NOT complementary?
A) 25° and 65°
B) 40° and 50°
C) 30° and 70°
D) 45° and 55°
The correct answer is D) 45° and 55°. Which pair of angles is NOT complementary — the answer is 45° and 55°.
Part B: Fill in the Blank
Write the correct answer on each line.
1. If an angle and its supplement are equal, each measures 90 degrees.
When two equal angles are supplementary they split 180° in half, so each must be 180° divided by 2 = 90°.
2. The supplement of the complement of 30° is 120 degrees.
First find the complement of 30°: 90° minus 30° = 60°. Then find the supplement of 60°: 180° minus 60° = 120°.
3. A right angle is divided into three angles: 20°, 35°, and x°. Then x = 35.
A right angle is 90°, so subtract the two known angles: 90° minus 20° minus 35° = 35° for the missing angle.
4. Two angles on a straight line are in the ratio 1 to 2. The larger angle is 120 degrees.
Angles on a straight line total 180°. In a 1:2 ratio the parts are 180° divided by 3 = 60° each, so the larger angle is 2 times 60° = 120°.
5. If angle P is 48° and angle Q is supplementary to P, then angle Q is 132 degrees.
Supplementary angles add to 180°, so angle Q = 180° minus 48° = 132°.