Build a linear or exponential model, and say what the numbers mean

Answer Key - Grade 9 Math Worksheet - Building Confidence

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

1. 1.

   Esme's art club has 8 posters at week 0. In the growth table, every arrow is + 6 posters. What model gives y after x weeks?

   y = 6x + 8
2. 2.

   A science video shows 200 yeast cells at hour 0. In Jun's growth table, every arrow is × 1.5. What model gives y after x hours?

   y = 200(1.5)^x
3. 3.

   Kira's pond tank has 50 duckweed plants at week 0. In the growth table, every arrow is × 3. What model gives y after x weeks?

   y = 50(3)^x
4. 4.

   Milo's food-drive box model is linear. The growth table has 30 at x = 0 and 42 at x = 1. What is the rate m on each arrow?

   12
5. 5.

   Noah's bus-club member model is exponential. The growth table has 80 at x = 0 and 100 at x = 1. What is the factor b on each arrow?

   1.25
6. 6.

   Pia's reading-log page model is linear. The growth table has 64 at x = 0 and 80 at x = 1. What is the rate m on each arrow?

   16
7. 7.

   Ren's class tracks its trip fund with y = 12x + 40, in dollars after x weeks. What does the 12 mean?

   • The fund has $12 after 12 weeks
   • The fund starts with $12
   • $12 is added each week
8. 8.

   Tala models the juice left in a jug with y = 250 − 15x, in mL after x minutes. What does the 250 mean?

   • 250 mL are poured out each minute
   • There are 250 mL after 15 minutes
   • There are 250 mL at the start
9. 9.

   A chess club's members follow y = 120(1.06)^x after x months. Zee asks: what does the 1.06 mean?

   • Members grow by 106% each month
   • Members grow by 6% each month
   • The club gains 1.06 members each month
10. 10.

    After a save-paper drive, Ari's school uses y = 2000(0.9)^x sheets a week, x weeks later. What does the 0.9 mean?

    • Paper use falls by 0.9 sheets each week
    • Paper use falls by 90% each week
    • Paper use falls by 10% each week