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Math lesson plan · 8th grade (Year 9 in England) · 45 minutes

When are two plans equal? Equations from real comparisons

Algebra

CCSS 8.EE.C.7.BEngland: KS3 AlgebraEngland: GCSE Foundation Algebra

Objective and success criteria

Students will: When are two plans equal? Equations from real comparisons.

  • 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: Solve equations with x on both sides

Leads to: the next skill in this area.

Materials: Balance scales or a balance drawing, Algebra tiles, Function machine cards, Mini whiteboards and pens, Printed student sheet (below).

Warm-up · 5 min

  • Quick retrieval from earlier learning (Solve equations with x on both sides). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Solve: −3x − 8 = 4x − 1 → x = -1Prompt: Add 3x to both sides so the x-term stays positive.
  2. Ben solved 5x + 1 = 4x − 4 by adding 4x to both sides. Explain the mistake by finding the correct value of x. → x = -5Prompt: To remove 4x from the right, you must SUBTRACT 4x.
  3. Solve: −4x − 11 = x + 24 → x = -7Prompt: Add 4x to both sides so the x-term stays positive.

Hook · 5 min

  • Show a "think of a number" puzzle and ask the class to work out the starting number.
  • Share the objective: When are two plans equal? Equations from real comparisons. Read the success criteria together.

I do: model it · 10 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: Gym A charges $33 to join plus $3 per visit. Gym B charges $6 to join plus $6 per visit. For how many visits do they cost the same?
  • Step 1: 33 − 6 = 6n − 3n
  • Step 2: 27 = 3n
  • Step 3: n = 9
  • Answer: 9
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 10 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. Gym A charges $52 to join plus $5 per visit. Gym B charges $4 to join plus $9 per visit. For how many visits do they cost the same? → 12Prompt: Write each cost for n visits/films and set them equal.
  2. Nia has $8 and saves $2 a week. Zoe has nothing yet and saves $4 a week. After how many weeks will they have the same amount? → 4Prompt: Write each person's total after w weeks and set them equal.

You do: independent practice · 10 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 · 5 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. Candle A is 38 cm tall and burns 2 cm per hour. Candle B is 35 cm tall and burns 1 cm per hour. After how many hours are they the same height? → 3Prompt: Write each candle's height after h hours and set them equal.
  2. Omar has $6 and saves $5 a week. Zoe has nothing yet and saves $6 a week. After how many weeks will they have the same amount? → 6Prompt: Write each person's total after w weeks and set them equal.

Watch out for

  • Doing an operation to one side of an equation but not the other.
  • Reading 3x as 3 + x, or thinking x always stands for one particular number.

Support and stretch

Support

  • Review first: Solve equations with x on both sides.
  • Use concrete materials: balance scales or a balance drawing.
  • 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-8.

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

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When are two plans equal? Equations from real comparisons

Name

Date

Score/ 8

  1. Question 1

    Candle A is 37 cm tall and burns 2 cm per hour. Candle B is 31 cm tall and burns 1 cm per hour. After how many hours are they the same height?

    Answer

  2. Question 2

    Gym A charges $57 to join plus $3 per visit. Gym B charges $9 to join plus $7 per visit. For how many visits do they cost the same?

    Answer

  3. Question 3

    Tariq has $20 and saves $5 a week. Priya has nothing yet and saves $7 a week. After how many weeks will they have the same amount?

    Answer

  4. Question 4

    Candle A is 25 cm tall and burns 2 cm per hour. Candle B is 21 cm tall and burns 1 cm per hour. After how many hours are they the same height?

    Answer

  5. Question 5

    Gym A charges $52 to join plus $2 per visit. Gym B charges $7 to join plus $7 per visit. For how many visits do they cost the same?

    Answer

  6. Question 6

    Priya has $8 and saves $4 a week. Chloe has nothing yet and saves $8 a week. After how many weeks will they have the same amount?

    Answer

  7. Question 7

    Candle A is 26 cm tall and burns 5 cm per hour. Candle B is 11 cm tall and burns 2 cm per hour. After how many hours are they the same height?

    Answer

  8. Question 8

    Gym A charges $8 to join plus $3 per visit. Gym B charges $0 to join plus $5 per visit. For how many visits do they cost the same?

    Answer

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Answer key: When are two plans equal? Equations from real comparisons

  1. 1. 6

  2. 2. 12

  3. 3. 10

  4. 4. 4

  5. 5. 9

  6. 6. 2

  7. 7. 5

  8. 8. 4