Complementary, Adjacent & Missing Angles Practice
Use the angle total first, then subtract the known angles. Work the set slowly, then play Angle Outpost for visual practice.
Try each missing angle, then open the answer.
1. Two complementary angles are 35° and x°. Find x.
55°. Complementary angles add to 90°, so x = 90 − 35 = 55.
2. Two adjacent angles form a right angle. One is 62°. What is the other?
28°. A right angle is 90°, so the missing angle is 90 − 62 = 28.
3. A straight line is split into angles of 118° and x°. Find x.
62°. Angles on a straight line add to 180°, so x = 180 − 118 = 62.
4. Two supplementary angles are 47° and x°. Find x.
133°. Supplementary angles add to 180°, so x = 180 − 47 = 133.
5. Angles around a point are 90°, 125°, 70°, and x°. Find x.
75°. Angles around a point add to 360°. The known angles total 285°, so x = 360 − 285 = 75.
6. A triangle has angles 50°, 60°, and x°. Find x.
70°. Triangle angles add to 180°. 50 + 60 = 110, so x = 180 − 110 = 70.
7. A triangle has angles 38°, 92°, and x°. Find x.
50°. 38 + 92 = 130, and 180 − 130 = 50.
8. A vertical angle is opposite a 74° angle. What is its measure?
74°. Vertical angles are equal, so the opposite angle is also 74°.
9. Two intersecting lines make one angle of 116°. What is the adjacent angle?
64°. Adjacent angles on intersecting lines form a straight line, so 180 − 116 = 64.
10. A straight angle is split into three adjacent angles: 40°, 65°, and x°. Find x.
75°. A straight angle is 180°. 40 + 65 = 105, so x = 180 − 105 = 75.
11. Around a point, three angles are 140°, 85°, and 95°. What is the fourth angle?
40°. The known angles total 320°, so the missing angle is 360 − 320 = 40.
12. Two angles are complementary. One angle is twice the other. What are the angles?
30° and 60°. Let the smaller angle be x, so x + 2x = 90. Then 3x = 90, so x = 30 and the other angle is 60.
13. Two angles are supplementary. One is 25° more than the other. Find both angles.
77.5° and 102.5°. Let the smaller angle be x. Then x + (x + 25) = 180, so 2x = 155 and x = 77.5.
14. In a triangle, two angles are 45° and 45°. What is the third angle?
90°. 45 + 45 = 90, and 180 − 90 = 90.
15. An angle of 132° is on a straight line with angle x°. What kind of angle is x?
x = 48°, so it is an acute angle. Straight-line angles add to 180°, and 180 − 132 = 48.
Missing angles questions
What is the difference between complementary and supplementary angles?
Complementary angles add to 90 degrees. Supplementary angles add to 180 degrees, including adjacent angles that form a straight line.
What does adjacent mean in angle problems?
Adjacent angles sit next to each other and share a side. If adjacent angles make a right angle, straight line, or full turn, use that total to find the missing angle.
How should my child solve missing angle problems?
First name the angle relationship: right angle, straight line, around a point, triangle, or vertical angles. Then subtract the known angles from the total.
Should this angle practice be timed?
No. Keep it untimed. The goal is to recognize the relationship and explain the subtraction, not to race.
Preparing for a gifted & talented test? Many tests like the CogAT® include reasoning problems like these — see free CogAT-style sample questions →