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1.The remains of an old campfire are unearthed and it is found that there is only 80% as much radioactive carbon-14 in the charcoal samples from the campfire as there is in modern living trees. If the half-life of carbon- 14 is 5730 years, how long ago did the campfire burn?

  • math -

    Po = Poe^kt

    1/2 = e^5730k

    Ln(1/2) = Lne^5730k

    Ln(1/2) = 5730k

    K = ln(1/2)/5730

    Poe^ln(1/2)/5730 *t

    .80P0 = Poe^ln(1/2)/5730 *t

    .8 = e^ln(1/5)/5730 t

    ln(.8) = ln(.5)/5730t lne

    ln(.8) = ln(.5)/ 5730 t

    t = 5730ln(.8)/ln(.5)

  • math -

    t=1844.65 years

  • math -

    found in an Egyptian pyramid contains 75% of its original carbon_14 which has about 5730 years as half-life.

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