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

Classify slopes: positive, negative, zero or undefined

Algebra

CCSS 8.F.B.4CCSS 8.F.B.5England: KS3 Algebra

Objective and success criteria

Students will: Classify slopes: positive, negative, zero or undefined.

  • 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: Slope (gradient) of a line

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 (Slope (gradient) of a line). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.

Hook · 5 min

  • Show a "think of a number" puzzle and ask the class to work out the starting number.
  • Share the objective: Classify slopes: positive, negative, zero or undefined. 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: What kind of slope would the graph have? The temperature of a fridge held at exactly 4 °C all day, against time.
  • Step 1: Zero
  • Answer: Zero
  • 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. What kind of slope would the graph have? The water left in a tank that drains at a steady rate. (Positive / Negative / Zero) → NegativePrompt: Does the quantity go up, go down or stay the same as time passes?
  2. What kind of slope would the graph have? Distance travelled by a car at a steady speed, against time. (Positive / Negative / Zero) → PositivePrompt: Does the quantity go up, go down or stay the same as time passes?

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. What kind of slope would the graph have? Distance travelled by a car at a steady speed, against time. (Positive / Negative / Zero) → PositivePrompt: Does the quantity go up, go down or stay the same as time passes?
  2. What kind of slope would the graph have? The water left in a tank that drains at a steady rate. (Positive / Negative / Zero) → NegativePrompt: Does the quantity go up, go down or stay the same as time passes?

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: Slope (gradient) of a line.
  • 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

eurekami

Classify slopes: positive, negative, zero or undefined

Name

Date

Score/ 8

  1. Question 1

    What kind of slope would the graph have? The battery left on a phone during a video call.

    • A. Positive
    • B. Negative
    • C. Zero

  2. Question 2

    What kind of slope does the line through (1, 1) and (3, 3) have?

    xy−66−12−66120(1, 1)(3, 3)
    • A. Positive
    • B. Negative
    • C. Zero
    • D. Undefined

  3. Question 3

    What kind of slope would the graph have? The temperature of a fridge held at exactly 4 °C all day, against time.

    • A. Positive
    • B. Negative
    • C. Zero

  4. Question 4

    What kind of slope does the line through (−4, 5) and (−3, 6) have?

    xy−66−12−66120(−4, 5)(−3, 6)
    • A. Positive
    • B. Negative
    • C. Zero
    • D. Undefined

  5. Question 5

    What kind of slope would the graph have? The water left in a tank that drains at a steady rate.

    • A. Positive
    • B. Negative
    • C. Zero

  6. Question 6

    What kind of slope does the line through (1, 0) and (6, 0) have?

    xy−66−12−66120(1, 0)(6, 0)
    • A. Positive
    • B. Negative
    • C. Zero
    • D. Undefined

  7. Question 7

    What kind of slope does the line through (3, −4) and (4, −9) have?

    xy−66−12−66120(3, −4)(4, −9)
    • A. Positive
    • B. Negative
    • C. Zero
    • D. Undefined

  8. Question 8

    What kind of slope would the graph have? The height of a plant that grows steadily over time.

    • A. Positive
    • B. Negative
    • C. Zero

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Answer key: Classify slopes: positive, negative, zero or undefined

  1. 1. B. Negative

  2. 2. A. Positive

  3. 3. C. Zero

  4. 4. A. Positive

  5. 5. B. Negative

  6. 6. C. Zero

  7. 7. B. Negative

  8. 8. A. Positive