Question

From the following figure, how many ways can you show that lines l and m are parallel?

At least 4 ways
One way
Two ways


Three ways

Answer 1

At least 4 ways

Explanation:

To show that two lines intercepted by a transversal are parallel, it is sufficient to show that:

• same side interior angles are supplementary (100°+80°=180°)
• interior alternate angles are congruent (80°=80°) Or (100°=100°)
• corresponding angles are congruent (80° or 100°)
• exterior alternate angles are congruent (80° or 100°)

We can do each of them in at least one way.

Therefore there is at least four ways

The first choice is correct.