CMClearMathAcademy

Parallel Lines and Transversals

A free Geometry lesson from the “Geometry Foundations” unit, with a worked example and practice problems including step-by-step solutions.

When a transversal crosses parallel lines, corresponding and alternate interior angles are congruent, while same-side interior angles are supplementary. In Geometry Foundations, students need to read the diagram, name the relationship, choose a theorem or formula, and justify why the result follows. The expanded practice now includes fluency, transfer, cumulative review, and proof-style reasoning so Geometry feels connected instead of isolated by topic.

What you'll learn

Why it matters: Road markings, rail tracks, and tiled floors create parallel-line angle patterns that designers use to keep layouts aligned.

Worked example

Problem. Parallel lines are cut by a transversal. One same-side interior angle is 118 degrees. Find the other.

  1. Same-side interior angles are supplementary.
  2. They add to 180 degrees.
  3. 180 - 118 = 62.
  4. Connect the result back to Parallel Lines and Transversals so the geometric relationship is explicit.

Answer: 62 degrees

Lesson preview: this page shows 5 practice items. The interactive activity contains 28 practice items and 15 quiz items (multiple choice and typed response). Counts include repeated prompts and variants.

Practice problems

1. Corresponding angles formed by parallel lines are...

Choices: Congruent · Supplementary · Always 90 degrees · Unrelated

Show solution
  1. Corresponding angles have equal measures.

Answer: Congruent

2. If a corresponding angle is 73 degrees, what is its match?

Show solution
  1. Corresponding angles are congruent.

Answer: 73

3. Alternate interior angles are 5x and 110 degrees. Find x.

Show solution
  1. Set 5x = 110.

Answer: 22

4. Same-side interior angles include 125 degrees. What is the other angle?

Show solution
  1. 180 - 125 = 55.

Answer: 55

5. Which angle pair is supplementary when lines are parallel?

Choices: Same-side interior · Alternate interior · Corresponding · Vertical

Show solution
  1. Same-side interior angles add to 180 degrees.

Answer: Same-side interior

Practice this interactively with instant feedback and an AI tutor.

Practice Parallel Lines and Transversals Take the free placement check

More Geometry lessons