Math lesson plan · 4th grade (Year 5 in England) · 30 minutes
Add and subtract angles that share a vertex
Geometry
CCSS 4.MD.C.7England: Y5 Geometry
Objective and success criteria
Students will: Add and subtract angles that share a vertex.
- 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: Angles: types and measuring
Leads to: Missing angles on a straight line and around a point
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 (Angles: types and measuring). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- What type of angle is 209°? (acute / right / obtuse / straight / reflex) → reflexPrompt: Compare with a right angle (90°) and a straight line (180°).
- Two angles together make a straight line. One is 18°. What is the other, in degrees? → 162Prompt: Angles on a straight line add up to 180°.
- A right angle is split into two parts. One part is 16°. What is the other part, in degrees? → 74Prompt: A right angle is 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: Add and subtract angles that share a vertex. 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: Angle ABD is 25° and angle DBC is 29°. They sit side by side to make angle ABC. What is angle ABC?
- Step 1: 25° + 29° = 54°
- Answer: 54
- 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.
- Angle ABD is 37° and angle DBC is 45°. They sit side by side to make angle ABC. What is angle ABC? → 82Prompt: The whole angle is made of the two parts.
- Angle PQR is 120°. Ray QS splits it into two angles. Angle PQS is 106°. What is angle SQR? → 14Prompt: The two parts add up to the whole angle.
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.
- A fan is opened so that 5 equal sections of 20° sit side by side. What angle does the open fan make? → 100Prompt: The angles join without gaps or overlaps.
- Angle ABD is 34° and angle DBC is 30°. They sit side by side to make angle ABC. What is angle ABC? → 64Prompt: The whole angle is made of the two parts.
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: Angles: types and measuring.
- 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: Missing angles on a straight line and around a point.
- 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-4.
Free lesson plan from eurekami.com/lesson-plan-builder