Grade 8 · Math

8th grade Use the fit line's equation to predict, and say what its slope and intercept mean worksheet

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Use the fit line's equation to predict, and say what its slope and intercept mean

Grade 8 Math Worksheet - Challenge Me

NameDate

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

Kira's class model is y = 4x + 30 for hours of practice a week (x) and quiz score (y). About how many hours of practice go with a score of 70?
Luz's bean plant model is y = 2.5x + 5, with x in days and y in cm. About how many days after planting does a plant reach 25 cm?
Milo's bike model is y = 3x + 6 for ride length in km (x) and time in minutes (y). About how long a ride, in km, takes 33 minutes?
Noah's sunflower model is y = 1.5x + 12 for days since planting (x) and height in cm (y). About how many days after planting does a sunflower reach 33 cm?
Pia's piano club drew a fit line through (2, 18) and (8, 36). What is the line's equation, written like y = 2x + 5?
Ren's sunflower fit line passes through (4, 20) and (10, 35). What is the line's equation, written like y = 2x + 5?
Tala's reading club drew a fit line through (5, 30) and (15, 50). What is the line's equation, written like y = 2x + 5?
Zee drew a fit line through (10, 24) and (30, 40) on a plot of walks. What is the line's equation, written like y = 2x + 5?
Ari's class model is y = 4x + 30 for hours of practice (x) and quiz score (y). With 5 more hours, about how many more points does it predict?
Bo's seedling model is y = 1.5x + 4, with x in days and y in cm. Over 10 more days, about how many centimeters taller does it predict a seedling grows?

8th grade Use the fit line's equation to predict, and say what its slope and intercept mean worksheet – printable — Print: 1 2 3 4 5 6

About this worksheet

Use the fit line's equation to predict, and say what its slope and intercept mean. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

I can use a fit line's equation, or the line on the grid, to predict about how much y goes with an x, and the other way round.
I can say what the slope means in the story ("about 4 more points for each extra hour"), and whether the intercept means anything.
I can find a fit line's slope from two of its points, and write its equation.

Standard: 8.SP.A.3

Words to know

linear model: A fit line and its rule, used to describe and predict.

prediction: What the model says y is about, for a chosen x.

slope: How much y tends to change for each 1 more x.

intercept (start): The line's y-value at x = 0, where it crosses the y-axis.

tends to: Usually, but not exactly, for every dot.

inside / past the data: Between the smallest and largest x in the plot / just beyond it.

Common mistakes

Your child used the slope but left out the starting amount, the number added at the end of the line's rule. Read the rule together as 'start at the added number, then add the slope for each step'.

Your child swapped the two numbers of the line's rule: the slope multiplies x, and the start is added. Ask together: which number changes with each step, and which one is there at the start?

Your child read the data dot instead of the fit line. A prediction comes from the line, which shows the pattern, not from one dot. Put a finger on the line together at that spot.

Questions parents ask

What is the most common mistake with use the fit line's equation to predict, and say what its slope and intercept mean?

Your child used the slope but left out the starting amount, the number added at the end of the line's rule. Read the rule together as 'start at the added number, then add the slope for each step'.

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.

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