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Homework Help: Continuously compounded interest

  1. Dec 15, 2008 #1
    1. The problem statement, all variables and given/known data
    I must give medication to a patient continuously, but at the same time the kidneys eliminate the 2,5 per cent of the medication. I need to have 90micrograms of medication at the end of 4 hours. The initial medication amount is zero.
    Normally, the limit of the compound intereset formula must be taken.

    2. Relevant equations
    The formula for continuous compounding is
    Mfinal = Minitial x e^(rt)

    3. The attempt at a solution
    Mfinal is 90, r is -0,025, t is four and I need to find Minitial. Or is r 0,975. I try to solve the equation. I feel that I must find the rate first, like ln(Mfinal/Minitial)/t; but I can't without the initial value. Please help.
  2. jcsd
  3. Dec 15, 2008 #2
    ok I sorted it out. sorry to bother.
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