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

Answer Key - Grade 8 Math Worksheet

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

1. 1.

   Kira's fit line for bean plants is y = 2.5x + 12, with x in days and y in cm. About how tall does it predict a plant is on day 8, in cm?

   32
2. 2.

   Luz's bike fit line is y = 0.6x + 5 (x in minutes, y in km). The data stop at 35 minutes. If the pattern keeps going, about how far is a 40-minute ride?

   29
3. 3.

   Milo's jump model is y = 1.2x + 20 (x: weeks of training, y: jumps per minute). Data end at week 45. If the pattern keeps going, about how many jumps at week 50?

   80
4. 4.

   Pia's team drew a fit line through (2, 30) and (10, 70) on its practice plot. For each 1 more minute of practice, about how many more points does the line show?

   5
5. 5.

   Ren's sunflower fit line passes through (4, 15) and (12, 35). For each 1 more day, about how many centimeters taller does the line show?

   2.5
6. 6.

   Tala's gym class plotted minutes of exercise against heartbeats in 10 seconds. The fit line passes through (5, 12) and (25, 20). For each 1 more minute, about how many more beats does it show?

   0.4
7. 7.

   Zee's baking club fit line goes through (10, 40) and (40, 100). For each 1 more minute of baking, about how many millimeters taller does the line show?

   2
8. 8.

   Ari's class fit y = 3x + 15 to hours of practice (x) and quiz score (y). What does the 15 mean, if anything?

   • The 15 means the score tends to go up about 15 points for each extra hour.
   • The 15 means a student with 0 hours of practice tends to score about 15.
   • The 15 has no real meaning here, because no one practices 0 hours.
9. 9.

   Bo's club fit y = 1.5x + 6 to days since seedlings were moved outside (x) and height in cm (y). What does the 6 mean, if anything?

   • The 6 has no real meaning here, because no seedling is outside for 0 days.
   • The 6 means a seedling tends to be about 6 cm tall the day it goes outside.
   • The 6 means a seedling tends to grow about 6 cm each day.
10. 10.

    Jun fit y = 0.5x + 2 to park trees: trunk width in cm (x) and height in meters (y). What does the 2 mean, if anything?

    • The 2 means a tree with a trunk 0 cm wide tends to be about 2 meters tall.
    • The 2 means a tree tends to grow about 2 meters taller for each extra centimeter of width.
    • The 2 has no real meaning here, because no tree has a trunk 0 cm wide.