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    majehlover's Avatar
    majehlover Posts: 1, Reputation: 1
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    #1

    Jun 14, 2009, 07:40 PM
    Half-life equation
    Radium-226 has a half life of 1660 years.How many years does it take a radium sample to decay to 55% of the original amount. Round to the nearest year.
    Please help me set up this equation!
    Perito's Avatar
    Perito Posts: 3,139, Reputation: 150
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    #2

    Jun 14, 2009, 08:23 PM

    here are some links:

    Effective half-life - Wikipedia, the free encyclopedia

    Radioactive decay - Wikipedia, the free encyclopedia

    The equation you want is

    (equation 1)

    where is the original amount of material present. is the time in the same units as the half-life, is the half-life.

    in your case

    Divide both sides of equation 1 by . Enter the data you have and solve for t.
    Unknown008's Avatar
    Unknown008 Posts: 8,076, Reputation: 723
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    #3

    Jun 15, 2009, 11:40 AM

    I got a negative answer... I I got it, you missed a 'minus' sign in front of your power of two Perito...

    What's happening to you today? Tired?
    galactus's Avatar
    galactus Posts: 2,271, Reputation: 282
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    #4

    Jun 15, 2009, 01:20 PM
    We can easily find k, the constant of proportionately, from the formula for half-life:



    Since we are given the half-life is 1660, all we need to do is solve for k.



    Now we can sub this into the equation and solve for t:



    Solve for t.
    bjones2379's Avatar
    bjones2379 Posts: 1, Reputation: 1
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    #5

    Nov 5, 2010, 07:38 AM
    Can u put this in simple terms for me
    Unknown008's Avatar
    Unknown008 Posts: 8,076, Reputation: 723
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    #6

    Nov 5, 2010, 07:42 AM
    Quote Originally Posted by bjones2379 View Post
    can u put this in simple terms for me
    What do you mean? You want to know how to find the answer to this question on half life? :confused:

    Or do you perhaps have another question?
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