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8th grade Write y = mx + b from a table, graph or story, and say what m and b mean worksheet

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Write y = mx + b from a table, graph or story, and say what m and b mean

Grade 8 Math Worksheet - Challenge Me

NameDate

Circle the best answer, or write your answer on the line.

  1. Read this first

    Use the table

    input: xoutput: y
    41
    -210
    24
  2. Ari's math-club table shows a line, with uneven steps and no row for x = 0. What rule, written as y = mx + b, gives every row?

  3. Jun draws a line on a grid with negative numbers. Points A and B are marked, but neither is on the y-axis. What rule, written as y = mx + b, gives this line?

  4. Water freezes at 32 °F (0 °C) and boils at 212 °F (100 °C). Milo wants a rule for any temperature. What rule gives F from C, as F = mC + b?

  5. Snow in Noah's yard melts steadily: 50 cm deep on day 2, 35 cm on day 7. Let x be days and y cm. What rule gives y, as y = mx + b?

  6. On a steady ride, Pia is 4 km from home at minute 10, 13 km at minute 40. Let x be minutes, y km. What rule gives y, as y = mx + b?

  7. Ren uses F = 1.8C + 32 to change °C into °F. What does the 1.8 tell you?

    • Each 1 °C warmer is 1.8 °F warmer
    • Water freezes at 1.8 °F
    • 1.8 °C is the same as 32 °F
  8. The snow in Tala's yard follows y = -3x + 56, its depth in cm after x days. What does the -3 tell you?

    • The snow was 3 cm deep at day 0
    • The snow gets 3 cm deeper with each passing day
    • The snow gets 3 cm less deep each day
    • The snow has melted completely after 3 days
  9. On a ride, Zee's distance from home follows y = 0.4x + 2, in km after x minutes. What does the 2 tell you?

    • Zee rides 2 km each minute
    • The ride takes 2 minutes
    • Zee was already 2 km from home at minute 0
  10. Esme makes up a story for y = -50x + 600, with x in hours. Which story fits the rule?

    • A bottle holds 50 mL, and 600 mL is drunk each hour
    • A bottle holds 600 mL, and 50 mL is drunk each hour
    • A bottle holds 600 mL, and 50 mL is added each hour
    • A bottle holds 650 mL in all
  11. Jun makes up a story for y = 1.5x + 4, with x in weeks. Which story fits the rule?

    • A plant is 1.5 cm tall and grows 4 cm each week
    • A seed starts at 0 cm and grows 1.5 cm each week
    • A plant is 4 cm tall and grows 1.5 cm each week
    • A plant is 5.5 cm tall and stops growing
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8th grade Write y = mx + b from a table, graph or story, and say what m and b mean worksheet – printable
Print: 123456

About this worksheet

Write y = mx + b from a table, graph or story, and say what m and b mean. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

  • I can write y = mx + b for a line from a table, from two points on a graph, or from a story, even when x = 0 is not shown.
  • I can say what the slope and the y-intercept mean in a story, with their units.
  • I can pick the story that fits a rule such as y = 5x + 20.

Standard: 8.F.B.4

Words to know

rule (equation of the line): y = mx + b: every row of the table obeys it.

slope m: Output change ÷ input change: the change for 1 more x.

y-intercept b: The output at x = 0: the start.

step back: Use the slope to work out the row for x = 0.

initial value: Another name for the start, b.

Common mistakes

Your child put the starting value where the slope goes. In y = 3x + 5, ask: which number is the change for each step, and which is the start?

Your child wrote the rule with only the slope, as if the line went through (0, 0).

Your child used an output from the middle of the table as the start.

What to say

Ask: what is y when x is 0?

Ask: what is y when x is 0?

Questions parents ask

What is the most common mistake with write y = mx + b from a table, graph or story, and say what m and b mean?

Your child put the starting value where the slope goes. In y = 3x + 5, ask: which number is the change for each step, and which is the start?

Are these 8th grade math worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

More grade 8 math

See all grade 8 math

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