Back to the lesson plan builder
Lesson length30 min45 min60 min
Questions🔀 New questions

Print the plan for yourself; the student sheet prints on its own page after it.

Math lesson plan · 7th grade (Year 8 in England) · 45 minutes

Find and fix mistakes in equation solutions

Algebra

CCSS 7.EE.B.4.AEngland: KS3 Algebra

Objective and success criteria

Students will: Find and fix mistakes in equation solutions.

  • 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 two-step equations with negative numbers

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 two-step equations with negative numbers). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Solve: −3x + 13 = 49 → x = -12Prompt: First undo the addition: subtract 13 on both sides.
  2. Solve: 1 − 4x = −39 → x = 10Prompt: Subtract 1 from both sides.
  3. Solve and check by substituting: 5x − 11 = 14 → x = 5Prompt: To undo − 11, do the opposite.

Hook · 5 min

  • Show a "think of a number" puzzle and ask the class to work out the starting number.
  • Share the objective: Find and fix mistakes in equation solutions. 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: Solving 3x + 6 = 3: Step 1: 3x = -3. Step 2: x = −1. Where is the first mistake?
  • Step 1: 3x = 3 − 6 = -3
  • Step 2: x = -3 ÷ 3 = −1
  • Step 3: No mistake
  • Answer: No mistake
  • 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. Solving 8x + 16 = 96: Step 1: 8x = 80. Step 2: x = 72. Where is the first mistake? (Step 1 / Step 2 / No mistake) → Step 2Prompt: Step 1 should undo + 16.
  2. Felix expanded 2(x + 2) = 24 as 2x + 2 = 24, which gives a wrong answer. What is the correct value of x? → x = 10Prompt: Felix forgot to multiply 2 by 2.

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. Solving 3x + 15 = 3: Step 1: 3x = -12. Step 2: x = -15. Where is the first mistake? (Step 1 / Step 2 / No mistake) → Step 2Prompt: Step 1 should undo + 15.
  2. Tariq expanded 5(x + 2) = 5 as 5x + 2 = 5, which gives a wrong answer. What is the correct value of x? → x = -1Prompt: Tariq forgot to multiply 2 by 5.

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 two-step equations with negative numbers.
  • 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-7.

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

eurekami

Find and fix mistakes in equation solutions

Name

Date

Score/ 8

  1. Question 1

    Solving 2x + 10 = 10: Step 1: 2x = 0. Step 2: x = 0. Where is the first mistake?

    • A. Step 1
    • B. Step 2
    • C. No mistake

  2. Question 2

    Ravi expanded 2(x + 9) = 32 as 2x + 9 = 32, which gives a wrong answer. What is the correct value of x?

    x =

  3. Question 3

    Solving 8x + 6 = -2: Step 1: 8x = 4. Step 2: x = 0.5. Where is the first mistake?

    • A. Step 1
    • B. Step 2
    • C. No mistake

  4. Question 4

    Ava expanded 6(x + 2) = 30 as 6x + 2 = 30, which gives a wrong answer. What is the correct value of x?

    x =

  5. Question 5

    Solving 7x + 2 = 23: Step 1: 7x = 25. Step 2: x = 3.57. Where is the first mistake?

    • A. Step 1
    • B. Step 2
    • C. No mistake

  6. Question 6

    Liam expanded 4(x + 3) = -4 as 4x + 3 = -4, which gives a wrong answer. What is the correct value of x?

    x =

  7. Question 7

    Solving 3x + 10 = -5: Step 1: 3x = -15. Step 2: x = −5. Where is the first mistake?

    • A. Step 1
    • B. Step 2
    • C. No mistake

  8. Question 8

    Zara expanded 5(x + 1) = 55 as 5x + 1 = 55, which gives a wrong answer. What is the correct value of x?

    x =

Free from eurekami.com

for the adult only

Answer key: Find and fix mistakes in equation solutions

  1. 1. C. No mistake

  2. 2. x = 7

  3. 3. A. Step 1

  4. 4. x = 3

  5. 5. A. Step 1

  6. 6. x = -4

  7. 7. C. No mistake

  8. 8. x = 10