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In 1933, Riatt found that the length \(L\) of haddock in centimeters as a function of the age \(t\) in years is given approximately by the formula $$ L=53-42.82 \times 0.82^{t} . $$ a. Calculate \(L(4)\) and explain what it means. b. Compare the average yearly rate of growth in length from age 5 to 10 years with the average yearly rate of growth from age 15 to 20 years. Explain in practical terms what this tells you about the way haddock grow. c. What is the longest haddock you would expect to find anywhere?

Short Answer

Expert verified
a. The length of a haddock at age 4 is approximately 33.63 cm. b. Haddock grow faster between ages 5-10 (1.736 cm/year) than ages 15-20 (0.536 cm/year). c. The longest haddock expected would be 53 cm.

Step by step solution

01

Calculate L(4)

Use the formula \( L=53-42.82 \times 0.82^{t} \) and substitute \( t = 4 \). \[ L(4) = 53 - 42.82 \times 0.82^{4} \]Calculate \( 0.82^{4} \), which is approximately \( 0.45212176 \).\[ 42.82 \times 0.45212176 \approx 19.367 \]Therefore,\[ L(4) = 53 - 19.367 = 33.633 \]The length of the haddock at age 4 is approximately 33.63 cm. This indicates how much the haddock has grown by age 4.
02

Calculate average rate of growth from age 5 to 10

To determine the average yearly rate of growth from age 5 to 10, calculate \( L(10) \) and \( L(5) \) using the formula, then find the difference and divide by 5.\[ L(5) = 53 - 42.82 \times 0.82^{5} \]\[ 0.82^{5} \approx 0.37088082 \]\[ L(5) = 53 - 42.82 \times 0.37088082 \approx 37.118 \]\[ L(10) = 53 - 42.82 \times 0.82^{10} \]\[ 0.82^{10} \approx 0.16815154 \]\[ L(10) = 53 - 42.82 \times 0.16815154 \approx 45.799 \]The increase in length from age 5 to 10 is \( 45.799 - 37.118 = 8.681 \, \text{cm} \).Divide by 5 to find the average yearly growth: \( 8.681 \, \text{cm} / 5 \approx 1.736 \, \text{cm/year} \).
03

Calculate average rate of growth from age 15 to 20

Similarly, calculate \( L(15) \) and \( L(20) \) to determine the average yearly growth rate from age 15 to 20.\[ L(15) = 53 - 42.82 \times 0.82^{15} \]\[ 0.82^{15} \approx 0.06309573 \]\[ L(15) = 53 - 42.82 \times 0.06309573 \approx 50.303 \]\[ L(20) = 53 - 42.82 \times 0.82^{20} \]\[ 0.82^{20} \approx 0.02371724 \]\[ L(20) = 53 - 42.82 \times 0.02371724 \approx 52.981 \]The increase in length from age 15 to 20 is \( 52.981 - 50.303 = 2.678 \, \text{cm} \).Divide by 5 to find the average yearly growth: \( 2.678 \, \text{cm} / 5 \approx 0.536 \, \text{cm/year} \).
04

Compare growth rates and provide practical implications

The average yearly rate of growth from age 5 to 10 is approximately 1.736 cm/year, while from age 15 to 20 it is 0.536 cm/year. This indicates that haddock grow much faster during their earlier years and the growth slows down significantly as they age.
05

Determine the maximum length

As \( t o ext{infinity} \), \( 0.82^{t} \to 0 \), causing the equation to simplify to \( L = 53 \). This means, theoretically, the longest haddock you would expect to find is 53 cm, as the factor multiplying 42.82 approaches zero.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Exponential Functions
Exponential functions are a type of mathematical expression where a constant base is raised to a variable exponent. These functions are characterized by their rapid increase or decrease, depending on the base value.
In the given exercise, the function for haddock growth: \[ L(t) = 53 - 42.82 \times 0.82^{t} \] is an example of a decreasing exponential function. Here, the base 0.82 is less than one, indicating that as time (\(t\)) progresses, the term \(0.82^{t}\) becomes smaller. This results in the growth factor \(42.82 \times 0.82^{t}\) shrinking, which in turn leads to the length \(L\) approaching the maximum limit of 53 cm. This is characteristic of many natural processes where growth slows as maturity is reached.

Exponential functions model scenarios where rates of change are proportional to the state of the system. In biology, such functions are prominent in modeling populations or growth processes, like the size of fish over time. They provide insightful predictions about future states when growth rates change consistently with time.
Growth Rate Analysis
Growth rate analysis involves examining how a particular quantity increases or decreases over time. For the haddock-length function, the problem entails comparing growth rates over different intervals, specifically from ages 5 to 10 and 15 to 20.
The calculated growth rate from age 5 to 10 showcases a more substantial growth of approximately 1.736 cm per year, compared to a much slower rate of 0.536 cm per year from age 15 to 20.
  • The initial rapid growth can be attributed to the fish needing to reach maturity.
  • As the fish age, the slowdown in growth indicates less of a need for rapid size increases, likely for reasons related to metabolic requirements or ecological factors.
By analyzing these growth rates, we can grasp practical aspects of haddock biology and ecology. The data suggests that significant growth occurs primarily in early years, emphasizing the importance of early life stages in their life cycle.
Function Modeling
Function modeling is a technique used to create a mathematical representation or "model" of a real-world scenario. This approach helps predict behavior under various conditions. In the haddock problem, the function: \[ L(t) = 53 - 42.82 \times 0.82^{t} \] serves as a model for predicting haddock length based on age.

Through modeling, one can extract several key insights:
  • It allows us to approximate future lengths of haddocks at any given age.
  • It helps determine physical limits, such as the maximum length of the haddock being capped at 53 cm as \(t\) approaches infinity.
  • It assists in understanding how external factors might alter growth rates, although that is not detailed in this specific formula.
Modeling can also be expanded by adjusting parameters to fit new data or explore different scenarios, providing a flexible tool for various scientific studies in marine biology and beyond.

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Most popular questions from this chapter

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