posted by marjani

a radioactive material is undergoing nuclear decay. After 40 minutes, 25% of the sample remains. What is the half-life of the sample

  1. DrBob222

    This is the long way but I would do this.
    ln(No/N) = kt
    No = 100 (just make up any number)
    N = 25 (25% of whatever you picked for No)
    k = solve for this
    t = 40 minutes.

    Then substitute k into
    k = 0.693/t1/2 and solve for t1/2.

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