# Pre Calculus

If a 25 mg sample of radioactive material decays to 18.4 mg in 5 years, how long will it take the sample to decay to 20.5 mg?

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1. 25*e^-5k = 18.4
So, k = ln(18.4/25)/-5 = 0.0613

So, now just solve for t in

25*e^-.0613t = 20.5

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posted by Steve
2. bcx xb

1. 0
posted by Anonymous

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