- A27° and 63°
- B40° and 60°
- C100° and 80°
- D55° and 45°
Step-by-Step Solution
Complementary angles add to 90°. 27 + 63 = 90°. The others give 100, 180, and 100.
Answer: A) 27° and 63°
Which of the following pairs of angles are complementary?
Class 7Lines and AnglesLines and Angles
Key idea: Parallel lines and a transversal
When a transversal crosses two **parallel** lines, eight angles form (four at each intersection). They come in special pairs:
- **Corresponding angles**: same position at each intersection (e.g. both top-left). **Equal**.
- **Alternate interior angles**: between the parallel lines, on opposite sides of the transversal. **Equal**.
- **Alternate exterior angles**: outside the parallel lines, on opposite sides of the transversal. **Equal**.
- **Co-interior (same-side interior) angles**: between the parallel lines, on the same side of the transversal. **Supplementary** (sum to 180°).
These are the rules you'll use most. Sketch the figure and label what you know — the rest follows quickly.
- **Corresponding angles**: same position at each intersection (e.g. both top-left). **Equal**.
- **Alternate interior angles**: between the parallel lines, on opposite sides of the transversal. **Equal**.
- **Alternate exterior angles**: outside the parallel lines, on opposite sides of the transversal. **Equal**.
- **Co-interior (same-side interior) angles**: between the parallel lines, on the same side of the transversal. **Supplementary** (sum to 180°).
These are the rules you'll use most. Sketch the figure and label what you know — the rest follows quickly.
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