4

Set 8: Exponential Functions (Advanced)

Explanation

Answer: A

A bacteria culture triples every 2 hours. Starting with 500 bacteria, how many are there after 8 hours?

A.

40,500

✓ Correct
B.

13,500

C.

4,500

D.

1,500

Detailed Explanation

Choice A is correct. Choice A is the correct answer. Apply the tripling pattern. 1. Tripling periods: 82=4\frac{8}{2} = 4 periods. 2. Formula: N(t)=500(3)t/2N(t) = 500(3)^{t/2} where t=8t = 8. 3. Calculate: N(8)=500(3)4=500(81)=40,500N(8) = 500(3)^4 = 500(81) = 40,500. Strategic Tip: 4 triplings = multiply by 34=813^4 = 81. Choice B is incorrect because this is after 3 triplings (6 hours). Choice C is incorrect because this is after 2 triplings (4 hours). Choice D is incorrect because this is after only 1 tripling (2 hours).

Key Steps:

The correct answer is 40,500

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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