7

Set 12: Exponential Functions

Explanation

Answer: A

An island's invasive species population follows P(t)=50001+49e0.4tP(t) = \frac{5000}{1 + 49e^{-0.4t}} where tt is years. What is the initial population?

A.

100

✓ Correct
B.

5,000

C.

50

D.

2,500

Detailed Explanation

Choice A is correct. Choice A is the correct answer. Evaluate the logistic function at t=0t=0. 1. Substitute: P(0)=50001+49e0=50001+49P(0) = \frac{5000}{1 + 49 e^0} = \frac{5000}{1 + 49}. 2. Simplify: P(0)=500050=100P(0) = \frac{5000}{50} = 100. 3. Result: Initial population is 100. Strategic Tip: For logistic P(t)=K1+AertP(t) = \frac{K}{1 + Ae^{-rt}}, initial value is K1+A\frac{K}{1+A}. Choice B is incorrect because this is the carrying capacity, not initial population. Choice C is incorrect because this is 1+A1 +A (the denominator at t=0t=0). Choice D is incorrect because this is half the carrying capacity.

Key Steps:

The correct answer is 100

Why others are wrong:
B: Choice B is incorrect and may result from a calculation error.
C: Choice C is incorrect and may result from a calculation error.
D: Choice D is incorrect and may result from a calculation error.

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