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Slope and proportions: 8th grade math

Proportional relationships as slope; connect to similar triangles. A free 8th grade lesson plan, a question set with answers and a printable sheet with its key. Copy it and make it yours.

Lesson plan

Goal

  • Students can do this: proportional relationships as slope; connect to similar triangles.

Teach (10 min)

  • Going right, a line that goes up has a positive slope and one that goes down has a negative slope.
  • A flat line has slope 0. A straight up and down line has an undefined slope, because its run is 0.
  • Work one example on the board while students say each step aloud, then do one together.

Practise (15 min)

  • Students work the printable sheet in pairs, then alone.
  • Or practise it as a game with no sign-up: https://peabody.kids/math/lines.slopeSign?lesson=8-lines-slopesign-1&at=8

Exit ticket (5 min)

  • Three questions on a slip:
  • 1. A line passes through (3, 2) and (0, 0). Is its slope positive, negative, zero or undefined?
  • 2. A line passes through (−1, 0) and (4, 0). Is its slope positive, negative, zero or undefined?
  • 3. A line passes through (2, 1) and (3, 2). Is its slope positive, negative, zero or undefined?

Question set

10 questions that read in words, easiest first. Questions that need a picture are on the printable sheet below.

  1. A line passes through (3, 2) and (0, 0). Is its slope positive, negative, zero or undefined?
  2. A line passes through (−1, 0) and (4, 0). Is its slope positive, negative, zero or undefined?
  3. A line passes through (2, 1) and (3, 2). Is its slope positive, negative, zero or undefined?
  4. A line passes through (6, 3) and (3, 3). Is its slope positive, negative, zero or undefined?
  5. A line passes through (5, 0) and (6, 1). Is its slope positive, negative, zero or undefined?
  6. A line passes through (1, 0) and (4, −3). Is its slope positive, negative, zero or undefined?
  7. A line passes through (−2, −1) and (1, −4). Is its slope positive, negative, zero or undefined?
  8. A line passes through (2, 1) and (2, −4). Is its slope positive, negative, zero or undefined?
  9. A line passes through (1, −3) and (4, −3). Is its slope positive, negative, zero or undefined?
  10. A line passes through (1, 0) and (3, 0). Is its slope positive, negative, zero or undefined?
Answers
  1. Positive
  2. Zero
  3. Positive
  4. Zero
  5. Positive
  6. Negative
  7. Negative
  8. Undefined
  9. Zero
  10. Zero

Printable sheet

Name: ____________________   Date: ____________

Slope and proportions (8th grade)

  1. Look at the line. Is its slope positive, negative, zero or undefined?
    −6−6−5−5−4−4−3−3−2−2−1−1112233445566xy
  2. Look at the line. Is its slope positive, negative, zero or undefined?
    −6−6−5−5−4−4−3−3−2−2−1−1112233445566xy
  3. Look at the line. Is its slope positive, negative, zero or undefined?
    −6−6−5−5−4−4−3−3−2−2−1−1112233445566xy
  4. Look at the line. Is its slope positive, negative, zero or undefined?
    −6−6−5−5−4−4−3−3−2−2−1−1112233445566xy
  5. A line passes through (−1, 4) and (−5, 5). Is its slope positive, negative, zero or undefined?
  6. A line passes through (−2, 3) and (−4, −1). Is its slope positive, negative, zero or undefined?
  7. A line passes through (−5, 5) and (−3, 5). Is its slope positive, negative, zero or undefined?
  8. A line passes through (−3, −5) and (−3, −2). Is its slope positive, negative, zero or undefined?
  9. A line passes through (4, 4) and (−1, 4). Is its slope positive, negative, zero or undefined?
  10. Look at the line. Is its slope positive, negative, zero or undefined?
    −6−6−5−5−4−4−3−3−2−2−1−1112233445566xy
  11. A line passes through (3, 1) and (2, 2). Is its slope positive, negative, zero or undefined?
  12. A line passes through (−3, −1) and (1, −1). Is its slope positive, negative, zero or undefined?
Key
  1. Negative
  2. Positive
  3. Positive
  4. Negative
  5. Negative
  6. Positive
  7. Zero
  8. Undefined
  9. Zero
  10. Undefined
  11. Negative
  12. Zero

Written by Peabody from its own skill pages. Free, no ads, no sign-in. Children can practise this on Peabody. More from teachers: teacher-shared resources.