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Class 7

Chapter 5: Parallel and Intersecting Lines

Two lines are parallel if they never meet. They intersect if they cross. When a transversal cuts two parallel lines, it makes pairs of equal angles (corresponding) and pairs that add to 180° (co-interior).

Learning outcomes

  • Identify parallel, intersecting & transversal lines
  • Use angle properties to solve problems

Activities

  • Geo-board angle exploration

Worked examples

Read through these first, then try the practice below.

  1. Example 1 — Vertically opposite

    Two lines cross. One angle is 70°. What is its vertically opposite angle?

    Solution: Vertically opposite angles are equal: 70°.

  2. Example 2 — Linear pair

    Two angles on a straight line add to 180°. One is 65°. What is the other?

    Solution: 180 − 65 = 115°.

Self-do practice

Question 1 of 3 · Score 0/0

Two lines meet. One angle is 40°. What is the vertically opposite angle?

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