ChalkHour

Year 9 Maths: Straight line graphs lesson pack

A complete, ready-to-teach KS3 lesson on straight line graphs. Below is a real sample of what ChalkHour makes: the full pack adds three levels of worksheet, model answers, a teaching explainer and print-ready PDF and Word files.

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Real sample

Straight Line Graphs (y = mx + c)

This lesson introduces students to the algebraic representation of straight line graphs. Students will learn the significance of the formula y = mx + c, how to calculate the gradient, and how to find the equation of a line from various pieces of information.

Learning objectives

  • Identify the gradient (m) and y-intercept (c) from the equation y = mx + c.
  • Calculate the gradient of a line from a graph or two given points.
  • Construct the equation of a straight line given its gradient and y-intercept or two points.
  • Recognise and use the condition for parallel lines.

Lesson plan (60 minutes)

  1. Introduction · 10 min

    Starter: Plotting coordinates and calculating basic 'rise over run' on a grid.

  2. Explaining concepts · 15 min

    Direct Instruction: Explaining y = mx + c, gradient, and y-intercept using the teaching section scripts.

  3. Guided Practice · 10 min

    Guided Practice: Working through the worked example as a class and identifying m and c from various equations.

  4. Independent Practice · 20 min

    Independent Practice: Students work through Support, Core, or Stretch worksheets based on confidence.

  5. Assessment/Review · 5 min

    Plenary: 8-question multiple choice quiz to assess understanding.

Key vocabulary

Gradient
The steepness of a line, calculated as the change in y divided by the change in x.
y-intercept
The point where a graph crosses the y-axis (where x = 0).
Parallel
Lines in the same plane that never intersect and have the same gradient.
Coefficient
The number that multiplies a variable (e.g., the 'm' in mx).
Constant
A fixed value that does not change (the 'c' in y = mx + c).

Core worksheet (first questions)

  1. Find m and c for: y = 3x - 4
  2. Find m and c for: y = 5 - 2x
  3. Find m and c for: y = 0.5x + 3
  4. A line has gradient -4 and passes through (0, 10). Write its equation.

Quiz (sample)

  1. 1. In the equation y = mx + c, what does 'm' represent?

    • A. y-intercept
    • B. Gradient
    • C. x-intercept
    • D. Origin

  2. 2. What is the y-intercept of the line y = 3x + 7?

    • A. (7, 0)
    • B. (0, -7)
    • C. (0, 7)
    • D. (7, 7)

  3. 3. What is the gradient of the line y = 5 - 2x?

    • A. 2
    • B. -2
    • C. 5
    • D. -5

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