Let's solve each of the problems on the worksheet using the concepts of
complementary and
supplementary angles.
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🔷 Definitions:
-
Complementary angles: Two angles that add up to
90°.
-
Supplementary angles: Two angles that add up to
180°.
We’ll use these relationships to find the missing angle in each diagram.
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🔹 Problem 1:
- Given: One angle is
20°, and there’s a
right angle (90°) symbol.
- This means the two angles together form a right angle → they are
complementary.
- So, missing angle = 90° – 20° =
70°
✔ Answer: 70°
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🔹 Problem 2:
- Given: One angle is
25°, and again, there’s a
right angle (90°) symbol.
- So, these two angles are complementary.
- Missing angle = 90° – 25° =
65°
✔ Answer: 65°
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🔹 Problem 3:
- Given: One angle is
45°, and there’s a
right angle (90°) symbol.
- Again, complementary angles.
- Missing angle = 90° – 45° =
45°
✔ Answer: 45°
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🔹 Problem 4:
- Given: One angle is
60°, and the two angles form a
straight line (180°).
- So, they are
supplementary.
- Missing angle = 180° – 60° =
120°
✔ Answer: 120°
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🔹 Problem 5:
- Given: One angle is
155°, forming a straight line → supplementary.
- Missing angle = 180° – 155° =
25°
✔ Answer: 25°
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🔹 Problem 6:
- Given: One angle is
95°, forming a straight line → supplementary.
- Missing angle = 180° – 95° =
85°
✔ Answer: 85°
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🔹 Problem 7:
- Given: One angle is
45°, and it forms a
straight line with the other angle → supplementary.
- But wait — look closely: The angle shown is
outside the triangle-like shape, but it's clearly part of a straight line.
- So, missing angle = 180° – 45° =
135°
✔ Answer: 135°
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✔ Final Answers:
| Problem | Answer |
|--------|--------|
| 1 | 70° |
| 2 | 65° |
| 3 | 45° |
| 4 | 120° |
| 5 | 25° |
| 6 | 85° |
| 7 | 135° |
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📌 Summary:
- Use
90° for
complementary angles (right angle symbol).
- Use
180° for
supplementary angles (straight line).
Let me know if you'd like this as a printable answer sheet!
Parent Tip: Review the logic above to help your child master the concept of supplementary angles worksheet.
