Chapter 3: Problem 59
For a particular salmon population, the relationship between the number \(S\) of spawners and the number \(R\) of offspring that survive to maturity is given by the formula $$R=\frac{4500 S}{S+500}$$ (a) Under what conditions is \(R>S ?\) (b) Find the number of spawners that would yield \(90 \%\) of the greatest possible number of offspring that survive to maturity. (c) Work part (b) with \(80 \%\) replacing \(90 \%\). (d) Compare the results for \(S\) and \(R\) (in terms of percentage increases) from parts (b) and (c).
Short Answer
Step by step solution
Identify the given formula
Condition for R > S
Find maximum R
Calculate 90% of maximum R
Calculate 80% of maximum R
Percentage Increase Calculation
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Calculus
- Differential Calculus helps us find how a function changes as its input changes.
- It involves finding "derivatives," which capture the rate of change of a function.
Inequalities
- We set up the inequality \(\frac{4500S}{S + 500} > S\) to find where the offspring outnumber the spawners.
- This leads us to the inequality \(S^2 - 4000S < 0\), which we solve to find the valid range for \(S\).
- The solution \(0 < S < 4000\) tells us the interval where the number of offspring will be more than the number of spawners.
Derivative
- In this scenario, we used the derivative of the function \(R(S) = \frac{4500S}{S + 500}\) to find the maximum number of offspring.
- Using the quotient rule, which is \(\frac{d}{dx}\left(\frac{u}{v}\right) = \frac{u'v - uv'}{v^2}\), we computed the derivative and set it equal to zero to find the critical points.
- The critical point at \(S = 4000\) indicated where the function achieves a maximum, confirming that increasing the spawners up to this point maximizes the offspring.
Optimization
- To find the maximum number of offspring, we calculated the derivative \(R'(S)\) and found when it is zero.
- The problem required finding the optimal number of spawners \(S\) that yields the greatest offspring, using calculus to locate this value.
- We also calculated specific spawner amounts to achieve a certain percentage (like 90% and 80%) of the maximum offspring, involving algebraic manipulation of the given formula.
Percentage Calculation
- In this exercise, the maximum possible offspring count needs to be adjusted to calculate for percentages like 90% and 80% of the total.
- We calculated 90% of 3600 to be 3240, and solved \(\frac{4500S}{S + 500} = 3240\) to find \(S\).
- The same process determined the spawner requirement for 80% as well, deriving specific values for practical decision-making.
- Our understanding of percentages also helped find the percent increase in spawners and offspring numbers, providing insights into the efficiency of adjustments.