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

Answer Key - Grade 8 Math Worksheet - Challenge Me

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

1. Read this first

   Use the table

   input: x	output: y
   5	13
   1	5
   8	19

2. 1.

   Bo'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?

   y = 2x + 3
3. 2.

   Esme'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?

   y = 0.75x + 3
4. 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?

   y = 3x ÷ 4 + 2
5. 4.

   Kira 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?

   y = -4x ÷ 3 + 4
6. 5.

   Luz 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?

   y = 2x − 9
7. 6.

   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?

   F = 1.8C + 32
8. 7.

   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?

   y = -3x + 56
9. 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 has melted completely after 3 days
   • The snow gets 3 cm less deep each day
10. 9.

    Bo makes up a story for y = 5x + 20, with x in days. Which story fits the rule?

    • A jar holds 25 beads, and none are added
    • A jar starts empty, and 5 beads are added each day
    • A jar starts with 5 beads, and 20 beads are added each day
    • A jar starts with 20 beads, and 5 beads are added each day
11. 10.

    Esme makes up a story for y = -50x + 600, with x in hours. Which story fits the rule?

    • A bottle holds 600 mL, and 50 mL is drunk each hour
    • A bottle holds 50 mL, and 600 mL is drunk each hour
    • A bottle holds 600 mL, and 50 mL is added each hour
    • A bottle holds 650 mL in all