Set 9: Exponential Functions

Choice A is correct. Choice A is the correct answer. Determine the number of half-lives. 1. Remaining: $\frac{25}{200} = \frac{1}{8} = (\frac{1}{2})^3$. 2. Half-lives: 3 half-lives have occurred. 3. Time: $3\times 88 = 264$ years. Strategic Tip: $\frac{1}{8}$ means 3 halvings: $50\% \to 25\% \to 12.5\%$. Choice B is incorrect because this is 2 half-lives (would leave 50 grams). Choice C is incorrect because this is 1 half-life (would leave 100 grams). Choice D is incorrect because this is 4 half-lives (would leave 12.5 grams).