college algebra

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In 4 years, 30% of a radioactive element decays. Find its half-life. (Round your answer to one decimal place.)
_____ yr

  • college algebra -

    (1/2)^(4/k) = 0.7
    Now just solve for k.

    Expect a number greater than 4, since if the half-life were 4, then 50% would decay in 4 years.

  • college algebra -

    In other words
    (1/2)^([Years]/X)=[% remaining]
    Solve for X

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