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A material has a half-life of 12 hours. If initially there are 4 grams of the material, how much is present after 8 hours?

I know the answer is 8/3, but how would you solve this using calculus? please help.

  • math -

    no need for calculus.
    the amount left after t hours is

    4 (1/2)^(t/12)
    when t=8, that is
    4 (1/2)^(2/3)
    = 2.52

    I think the 8/3 = 2.67 answer is bogus. Close, but nowhere near exact. 8 is 2/3 of 12, but that's not how half-lives work.

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