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🧩 8th grade math · Patterns & Algebra

Slope and proportions

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.

Worked example

Look at the line. Is its slope positive, negative, zero or undefined?
−6−6−5−5−4−4−3−3−2−2−1−1112233445566xy
Answer: Positive
The line goes up as you move right, so the slope is positive. Answer: Positive.

For grown-ups: Proportional relationships as slope; connect to similar triangles. Below: three problems to try with the worked answers, and a free printable sheet. Children can practise the same skill as a game, with no sign-up and no ads.

  • CCSS 8.EE.B.5–6
What this practises, for teachers

Practices proportional relationships as slope; connect to similar triangles (8.EE.B.5–6). A printable sheet with its answer key, worked answers on the page, no accounts.

▶ Practise it

For your class

🖨️ Printable sheet and key

Try three

  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
    Show the answer and how
    Answer: Negative
    The line goes down as you move right, so the slope is negative. Answer: Negative.
  2. A line passes through (1, 2) and (−2, 3). Is its slope positive, negative, zero or undefined?
    Show the answer and how
    Answer: Negative
    Go from (1, 2) to (−2, 3): run −3, rise 1. The line goes down as you move right, so the slope is negative. Answer: Negative.
  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
    Show the answer and how
    Answer: Positive
    The line goes up as you move right, so the slope is positive. Answer: Positive.

Before and after

Learn first: Scale drawings (7th)

Name: ____________________Date: ____________Score: ____ / 12

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?

Answer 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

More 8th grade skills: all 8th grade math skills, or every grade at math skills.