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advanced-math

A population model is P(t)=500001+Ae0.8tP(t) = \frac{50000}{1 + Ae^{-0.8t}}. If P(0)=5000P(0) = 5000, what is AA?

A

A=9A = 9

B

A=10A = 10

C

A=5A = 5

D

A=45A = 45

Correct Answer: A

Choice A is the correct answer. Use the initial condition to find AA.

  1. At t=0t=0: 5000=500001+Ae0=500001+A5000 = \frac{50000}{1 + Ae^0} = \frac{50000}{1 + A}.
  2. Multiply: 5000(1+A)=500005000(1 + A) = 50000.
  3. Divide: 1+A=101 + A = 10.
  4. Solve: A=9A = 9.
  5. Verify: P(0)=500001+9=5000P(0) = \frac{50000}{1 + 9} = 5000

💡 Strategic Tip: Initial condition gives P0=K1+AP_0 = \frac{K}{1+A}, so A=KP01A = \frac{K}{P_0} - 1.

Choice B is incorrect because this would give P(0)=50000114545P(0) = \frac{50000}{11} \approx 4545. Choice C is incorrect because this would give P(0)=5000068333P(0) = \frac{50000}{6} \approx 8333. Choice D is incorrect because this would give P(0)=50000461087P(0) = \frac{50000}{46} \approx 1087.