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Choice D) 281.25 mg

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Work Shown:

Plug in t = 2 and we get the following

The answer is choice D. There are 281.25 mg of aspirin in the bloodstream after 2 hours.

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Side notes:

The 500 represents the initial amount of aspirin (in mg) in the bloodstream. This is the amount when t = 0.The 3/4 converts to 0.75; when solving 1+r = 0.75, we get r = -0.25, and this shows a 25% reduction in aspirin each time t goes up by 1. Every hour, the amount of aspirin in the bloodstream reduces by 25%

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since the cosine is the ratio of the adjacent side to the hypotenuse, you can see that cos 60° = ½. answer. according to the property of cofunctions (topic 3), sin 30° is equal to cos 60°. sin 30° = ½.