Let's solve each of the four problems step by step using the properties of
parallel lines and a
transversal.
We are told:
- Lines A and B are
parallel.
- Line C is a
transversal (a line that crosses two or more lines).
- We'll use angle relationships such as:
-
Corresponding angles are equal.
-
Alternate interior angles are equal.
-
Alternate exterior angles are equal.
-
Consecutive interior angles (same-side interior) add up to 180°.
-
Vertical angles are equal.
-
Supplementary angles add up to 180°.
---
🔷 Problem 1:
Given:
Angle at the top = 85°
Lines A || B, transversal C
We need to find:
- Angle 1
- Angle 2
Step-by-step:
- The 85° angle and
Angle 1 are
vertical angles → they are equal.
→ So,
Angle 1 = 85°
- Now,
Angle 1 and
Angle 2 are
alternate interior angles (since lines A and B are parallel), so they are equal.
→
Angle 2 = 85°
✔ Answer:
- Angle 1 =
85°
- Angle 2 =
85°
---
🔷 Problem 2:
Given:
Angle between transversal and lower line B = 122°
We need to find:
- Angle 1
- Angle 2
Step-by-step:
- The given 122° angle is on line B, and it’s adjacent to
Angle 2.
→ They form a straight line → supplementary → sum = 180°
→ So,
Angle 2 = 180° – 122° = 58°
- Now,
Angle 1 and the 122° angle are
corresponding angles (they are in the same relative position at the intersection with A and B).
→ Since A || B, corresponding angles are equal.
→ So,
Angle 1 = 122°
✔ Answer:
- Angle 1 =
122°
- Angle 2 =
58°
---
🔷 Problem 3:
Given:
Angle at top = 72°
We need to find:
- Angle 1
- Angle 2
Step-by-step:
- The 72° angle and
Angle 1 are
alternate interior angles (they are on opposite sides of the transversal and inside the parallel lines).
→ So,
Angle 1 = 72°
- Now,
Angle 1 and
Angle 2 are
adjacent angles forming a straight line → supplementary.
→ So,
Angle 2 = 180° – 72° = 108°
✔ Answer:
- Angle 1 =
72°
- Angle 2 =
108°
---
🔷 Problem 4:
Given:
Angle below line B = 140°
We need to find:
- Angle 1
- Angle 2
Step-by-step:
- The 140° angle and
Angle 2 are
vertical angles → equal.
→ So,
Angle 2 = 140°
- Now,
Angle 1 and the 140° angle are
consecutive interior angles (on the same side of the transversal, between the parallel lines).
→ They are supplementary → sum = 180°
→ So,
Angle 1 = 180° – 140° = 40°
✔ Answer:
- Angle 1 =
40°
- Angle 2 =
140°
---
✔ Final Answers:
| Problem | Angle 1 | Angle 2 |
|--------|---------|---------|
| 1 | 85° | 85° |
| 2 | 122° | 58° |
| 3 | 72° | 108° |
| 4 | 40° | 140° |
---
📌 Summary of Key Concepts Used:
-
Vertical angles: Equal
-
Corresponding angles: Equal (when lines are parallel)
-
Alternate interior angles: Equal
-
Same-side interior angles: Add to 180°
-
Straight line angles: Add to 180°
Let me know if you'd like a diagram explanation or printable version!
Parent Tip: Review the logic above to help your child master the concept of angles in parallel lines worksheet.