SOLUTION: The half-life of aspirin in your bloodstream is 12 hours. How long will it take for the aspirin to decay to 80% of the original dosage?

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Question 399126: The half-life of aspirin in your bloodstream is 12 hours. How long will it take for the aspirin to decay to 80% of the original dosage?
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
B+=+P%2A%281%2F2%29%5E%28t%2F12%29 ==> 0.80P+=+P%2A%281%2F2%29%5E%28t%2F12%29
==> 0.80++=+%281%2F2%29%5E%28t%2F12%29 ==> ln0.80%2Fln%281%2F2%29+=+t%2F12
==> t+=+%2812%2Aln0.80%29%2Fln%281%2F2%29+=+3.86 hours, to 3 decimal places.