1. A drug's effectiveness decreases over time. If each hour, a drug is only 90% as effective as during the previous hour, at some point the patient will not be receiving enough medication and will...

Extracted text: 1. A drug's effectiveness decreases over time. If each hour, a drug is only 90% as effective as during the previous hour, at some point the patient will not be receiving enough medication and will need another dose. This can be modeled by the exponential function y= y,(0.90). In this equation y, is the amount of the %3D initial dose, and y is the amount of the medication still available "t" hours after the drug was administered. Suppose the initial dose was 200 mg. How long will it take for this initial dose to reach the dangerously low level of 50 mg? Solve this problem algebraically, not with a graph or by plugging and checking.