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.

   Bo's bean plant is 20 cm tall at week 0. In the growth table, every arrow is + 3 cm. What model gives y after x weeks?

   y = 3x + 20
2. 2.

   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
3. 3.

   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
4. 4.

   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
5. 5.

   Luz's flower-count model is exponential. The growth table has 20 at x = 0 and 50 at x = 1. What is the factor b on each arrow?

   2.5
6. 6.

   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
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
   • The club gains 1.06 members each month
   • Members grow by 6% 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 90% each week
    • Paper use falls by 10% each week
    • Paper use falls by 0.9 sheets each week