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Math lesson plan · 5th grade (Year 6 in England) · 30 minutes

Reflect points in a horizontal or vertical mirror line

Geometry

CCSS 8.G.A.1England: Y5 GeometryEngland: Y6 Geometry

Objective and success criteria

Students will: Reflect points in a horizontal or vertical mirror line.

  • 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: Lines of symmetry; Coordinates in the first quadrant

Leads to: the next skill in this area.

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 (Lines of symmetry; Coordinates in the first quadrant). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. How many lines of symmetry does an equilateral triangle have? → 3Prompt: A line of symmetry folds the shape into two matching halves.
  2. Which capital letter has a vertical line of symmetry: O, P, S, J? (O / S / P / J) → OPrompt: Imagine a mirror standing straight up through the middle of the letter.
  3. How many lines of symmetry does a square have? → 4Prompt: A line of symmetry folds the shape into two matching halves.

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: Reflect points in a horizontal or vertical mirror line. 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.
  • Model one question from the student sheet, thinking aloud.
  • 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.

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.

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: Lines of symmetry.
  • 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

  • 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-5.

Free lesson plan from eurekami.com/lesson-plan-builder

eurekami

Reflect points in a horizontal or vertical mirror line

Name

Date

Score/ 6

  1. Question 1

    Reflect the point (1, 8) in the vertical line x = 5. Where is its image?

    xy12345678910123456789100P

    Answer

  2. Question 2

    A point is reflected in the line x = 5 and its image is at (9, 2). Where was the original point?

    xy12345678910123456789100P′

    Answer

  3. Question 3

    Reflect the point (7, 10) in the horizontal line y = 5. Where is its image?

    xy12345678910123456789100P

    Answer

  4. Question 4

    Reflect the point (2, 1) in the horizontal line y = 3. Where is its image?

    xy12345678910123456789100P

    Answer

  5. Question 5

    A point is reflected in the line x = 5 and its image is at (9, 1). Where was the original point?

    xy12345678910123456789100P′

    Answer

  6. Question 6

    Reflect the point (0, 9) in the vertical line x = 3. Where is its image?

    xy12345678910123456789100P

    Answer

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Answer key: Reflect points in a horizontal or vertical mirror line

  1. 1. (9, 8)

  2. 2. (1, 2)

  3. 3. (7, 0)

  4. 4. (2, 5)

  5. 5. (1, 1)

  6. 6. (6, 9)