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

Slope (gradient) of a line

Algebra

CCSS 8.EE.B.5CCSS 8.EE.B.6CCSS 8.F.B.4England: KS3 AlgebraEngland: GCSE Foundation Algebra

Objective and success criteria

Students will: Slope (gradient) of a 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: Coordinates in all four quadrants; Proportional relationships; Equivalent fractions

Leads to: Scatter graphs and correlation; Graphs of linear equations y = mx + b; Find the slope from a graph using rise over run

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 (Coordinates in all four quadrants; Proportional relationships; Equivalent fractions). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Is this relationship proportional? x: 3, 4, 8 → y: 27, 37, 72 (Yes, proportional / No, not proportional) → No, not proportionalPrompt: Find y ÷ x for each pair.
  2. Is this relationship proportional? x: 1, 3, 8 → y: 8, 25, 64 (Yes, proportional / No, not proportional) → No, not proportionalPrompt: Find y ÷ x for each pair.
  3. Is this relationship proportional? x: 4, 8, 10 → y: 12, 25, 30 (Yes, proportional / No, not proportional) → No, not proportionalPrompt: Find y ÷ x for each pair.

Hook · 5 min

  • Show a "think of a number" puzzle and ask the class to work out the starting number.
  • Share the objective: Slope (gradient) of a line. 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.
  • 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 · 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.

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.

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: Coordinates in all four quadrants.
  • 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

  • Move on to: Scatter graphs and correlation; Graphs of linear equations y = mx + b; Find the slope from a graph using rise over run.
  • 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

Slope (gradient) of a line

Name

Date

Score/ 8

  1. Question 1

    Find the slope (gradient) of the line through (3, −2) and (6, −10). Give a whole number or a fraction in simplest form.

    xy−12−6612−12−66120AB

    Answer(as a fraction)

  2. Question 2

    The line passes through the two marked points (0, 2) and (2, −2). What is its slope?

    xy−66−12−66120y = −2x + 2AB

    Answer

  3. Question 3

    Lucia cycles at a steady speed. The graph of distance (km) against time (hours) passes through (0, 0) and (8, 88). What is the slope, and so the speed in km/h?

    xy12345678910660y = 11x(8, 88)

    Answer

  4. Question 4

    Find the slope (gradient) of the line through (−6, −3) and (−2, −5). Give a whole number or a fraction in simplest form.

    xy−12−6612−12−66120AB

    Answer(as a fraction)

  5. Question 5

    The line passes through the two marked points (0, 0) and (2, 2). What is its slope?

    xy−66−12−66120y = xAB

    Answer

  6. Question 6

    Maya cycles at a steady speed. The graph of distance (km) against time (hours) passes through (0, 0) and (5, 10). What is the slope, and so the speed in km/h?

    xy24681024681012141618200y = 2x(5, 10)

    Answer

  7. Question 7

    Find the slope (gradient) of the line through (−5, −5) and (−7, −3). Give a whole number or a fraction in simplest form.

    xy−12−6612−12−66120AB

    Answer(as a fraction)

  8. Question 8

    The line passes through the two marked points (0, −1) and (2, 3). What is its slope?

    xy−66−12−66120y = 2x − 1AB

    Answer

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Answer key: Slope (gradient) of a line

  1. 1. -8/3

  2. 2. -2

  3. 3. 11

  4. 4. -1/2

  5. 5. 1

  6. 6. 2

  7. 7. -1

  8. 8. 2