1. Warm-Up
Solve for x:
1. 3x + 2 + 2x + 4 = 56
2. 9x + 4 + 3x – 4 = 120

2. Essential Question
What are parallel lines? What is a transversal?

3. Angles with Lunch Lines
Unit 1, Day 15

4. Common Core GPS
MCC8. G. 5: Use informal arguments to
establish facts about the angle sum and
exterior angle of triangles, about the angles
created when parallel lines are cut by a
transversal, and the angle-angle criterion for
similarity of triangles.

5. Language of the Standards
Alternate Interior Angles: pairs of angles formed when a
third line (a transversal) crosses two other lines. These
angles are on opposite sides of the transversal and are
in between the other two lines. When the two other
lines are parallel, the alternate interior angles are
equal.
Linear Pair: adjacent, supplementary angles. A linear
pair forms a straight line.
Same-side Interior angles: pairs of angles formed when
a third line (a transversal) crosses two other lines.
These angles are on the same side of the transversal
and are between the other two lines. When the two
other lines are parallel, same-side interiorr angles are
supplementary.

6. Same-side Exterior Angles: pairs of angles
formed when a third line (a transversal)
crosses two other lines. These angles are on
the same side of the transversal and are
outside the other two lines. When the two
other lines are parallel, same-side exterior
angles are supplementary.
Transversal: a line that crosses two or more
lines.

7. Parallel Lines
Parallel lines are lines that _______________.
Special angles are formed when parallel lines are
crossed by a transversal.

8. Angles
Let’s label and name the special angles.

9. Angle measurements
Some of the angles are congruent while others
are supplementary.

10. What is the value of x?

11. What is the value of x?

12. What is the value of x?

13. Find the measurement of <2.

14. Work Session: Lunch Lines
Paul, Jane, Justin, Sarah, and Opal were finished
with lunch and began playing with drink straws.
Each one was making a line design using either 3
or 4 straws. They had just come from math class
where they had been studying special angles.
Paul pulled his pencil out of his book bag and
labeled some of the angles and lines. He then
challenged himself and the others to find all the
labeled angle measurements and to determine
whether the lines that appear to be parallel really
could be parallel.

16. 1.
Find all of the
labeled angle
measurements,
assuming the lines
that appear parallel
are parallel.
2.
Determine whether
the lines that appear
to be parallel really
could be parallel.
3. Explain the reasoning for
your results.

17. Closing:
What have you learned about parallel lines
crossed by a transversal?
Did this task help you understand the “special
angles” and their relationships?
What did you struggle with while completing
this task?