MathBench > Population Dynamics

Exponential Growth and Decay

Coffee and bookCaffeine withdrawal

Another familiar drug, caffeine, decreases in your body by 12% per hour. If you’re planning to drink a cup before a long exam it might be very useful to know how long it takes for the caffeine to diminish before you to need more to stay alert. 




If you start with a standard cup of coffee containing 120mg of caffeine, how long before the effects wear off? (Note: You might be affected by as little as 50 mg)

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I think I have the answer: 120×0.887 = 49mg, so about 7 hours.