Math lesson plan · 8th grade (Year 9 in England) · 30 minutes
Angles with parallel lines
Geometry
CCSS 8.G.A.5England: KS3 GeometryEngland: GCSE Foundation Geometry
Objective and success criteria
Students will: Angles with parallel lines.
- I can answer questions on today's skill on my own, without help.
- I can explain each step and say why it works.
- I can check my answer and spot a mistake.
Before and after
Needs first: Vertical, complementary and supplementary angles
Leads to: Circle theorems; Name and use angle pairs on parallel lines; Give the reason for each step in an angle argument
Materials: Rulers and protractors, Squared or dotted paper, Shape cut-outs, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 4 min
- Quick retrieval from earlier learning (Vertical, complementary and supplementary angles). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- What is the complement of 34°? → 56Prompt: Complementary angles add up to 90°.
- Two angles on a straight line are (2x + 20)° and 128°. Find x. → x = 16Prompt: Angles on a straight line add up to 180°.
- What is the complement of 30°? → 60Prompt: Complementary angles add up to 90°.
Hook · 3 min
- Show a photo of a building, a tile pattern or a road sign and ask what shapes and angles students can spot.
- Share the objective: Angles with parallel lines. Read the success criteria together.
I do: model it · 7 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: A line crosses two parallel lines. One angle is 32°. What is the corresponding angle to it, in degrees?
- Step 1: Corresponding angles are equal: 32°.
- Answer: 32
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 6 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- A line crosses two parallel lines. One angle is 40°. What is the alternate angle to it, in degrees? → 40Prompt: Alternate angles are equal (Z shape). Corresponding angles are equal (F shape).
- Alternate angles on parallel lines are (3x + 13)° and 58°. Find x. → x = 15Prompt: Alternate angles are equal.
You do: independent practice · 7 min
- Students work on the student sheet. Circulate and check the first two answers of every student early.
- Students who finish: write a question of their own for a partner, with the answer.
The 6 questions are on the student sheet below, with answers in the key.
Exit ticket · 3 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- Alternate angles on parallel lines are (3x + 22)° and 112°. Find x. → x = 30Prompt: Alternate angles are equal.
- A line crosses two parallel lines. One angle is 50°. What is the alternate angle to it, in degrees? → 50Prompt: Alternate angles are equal (Z shape). Corresponding angles are equal (F shape).
Watch out for
- Thinking a square turned on its corner is no longer a square.
- Reading the wrong scale on a protractor.
Support and stretch
Support
- Review first: Vertical, complementary and supplementary angles.
- Use concrete materials: rulers and protractors.
- Give the first step of each question, or a partly worked example to finish.
- Pair with a confident partner for the guided practice.
Stretch
- Move on to: Circle theorems; Name and use angle pairs on parallel lines; Give the reason for each step in an angle argument.
- Explain a common mistake in writing and how to fix it.
- Write a word problem that uses today's skill, then solve a partner's.
Homework and more practice
Free online practice with hints and printable worksheets for this skill: eurekami.com/math/grade-8.
Free lesson plan from eurekami.com/lesson-plan-builder