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Modelling Growth & Decay with Recursion (Grade 11)

Free printable Grade 11 General Mathematics worksheet: modelling real growth and decay (savings, populations, depreciation, managed populations) with arithmetic, geometric and first-order linear recurrence relations (ACMGM070, ACMGM074, ACMGM077).

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Grade 11 · Math worksheet
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Growth & Decay: Modelling with Recursion

Set up a recurrence relation for each real situation and compute the requested term. Linear (equal step) situations use arithmetic sequences; constant-factor growth or decay uses geometric sequences; a survival-plus-restock situation uses a first-order linear recurrence.

  1. 1.
    A savings account starts with $175 and $39 is added every week. Model the balance with a recurrence relation and find the balance after 5 weeks.
  2. 2.
    A savings account starts with $350 and $35 is added every week. Model the balance with a recurrence relation and find the balance after 5 weeks.
  3. 3.
    A savings account starts with $380 and $35 is added every week. Model the balance with a recurrence relation and find the balance after 5 weeks.
  4. 4.
    A bacterial colony starts at 155 cells and multiplies by 2 every hour. Model it with a recurrence relation and find the population after 4 hours.
  5. 5.
    A bacterial colony starts at 145 cells and multiplies by 3 every hour. Model it with a recurrence relation and find the population after 3 hours.
  6. 6.
    A bacterial colony starts at 150 cells and multiplies by 2 every hour. Model it with a recurrence relation and find the population after 3 hours.
  7. 7.
    A car worth $50000 loses 20% of its value each year (so it keeps 80%). Model the value with a recurrence relation and find its value after 4 years. Round to the nearest cent.
  8. 8.
    A car worth $36000 loses 20% of its value each year (so it keeps 80%). Model the value with a recurrence relation and find its value after 3 years. Round to the nearest cent.
  9. 9.
    A car worth $38000 loses 50% of its value each year (so it keeps 50%). Model the value with a recurrence relation and find its value after 3 years. Round to the nearest cent.
  10. 10.
    A trout lake starts with 213 fish. Each year 90% survive and 55 new fish are added. Model this with a first-order linear recurrence and find the number of fish after 4 years. Round to the nearest whole fish.
  11. 11.
    A trout lake starts with 451 fish. Each year 90% survive and 150 new fish are added. Model this with a first-order linear recurrence and find the number of fish after 3 years. Round to the nearest whole fish.
  12. 12.
    A trout lake starts with 287 fish. Each year 80% survive and 147 new fish are added. Model this with a first-order linear recurrence and find the number of fish after 2 years. Round to the nearest whole fish.
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