Math lesson plan · 6th grade (Year 7 in England) · 60 minutes
Area of triangles
Geometry
CCSS 6.G.A.1England: Y6 MeasurementEngland: KS3 Geometry
Objective and success criteria
Students will: Area of triangles.
- 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: Area of rectangles; Classify triangles; angles in a triangle
Leads to: Area of parallelograms and trapezoids; Surface area using nets; Volume of prisms
Materials: Rulers and protractors, Squared or dotted paper, Shape cut-outs, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 6 min
- Quick retrieval from earlier learning (Area of rectangles; Classify triangles; angles in a triangle). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
Hook · 6 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: Area of triangles. Read the success criteria together.
I do: model it · 12 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: A triangle has area 16 yd² and base 8 yd. What is its height, in yd?
- Step 1: 2 × 16 = 32
- Step 2: 32 ÷ 8 = 4 yd
- Answer: 4
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 12 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 triangle has area 88 cm² and base 16 cm. What is its height, in cm? → 11Prompt: Area = ½ × base × height.
- A triangle has area 84 cm² and base 14 cm. What is its height, in cm? → 12Prompt: Area = ½ × base × height.
You do: independent practice · 17 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 8 questions are on the student sheet below, with answers in the key.
Exit ticket · 7 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- A triangle has area 54 m² and base 9 m. What is its height, in m? → 12Prompt: Area = ½ × base × height.
- A triangle has area 75 cm² and base 15 cm. What is its height, in cm? → 10Prompt: Area = ½ × base × height.
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: Area of rectangles.
- 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: Area of parallelograms and trapezoids; Surface area using nets; Volume of prisms.
- 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-6.
Free lesson plan from eurekami.com/lesson-plan-builder