document.write( "Question 822995: Use Q(t)=Q sub 0 e^kt to solve: Find the half-life of a radioactive substance if 240 grams of the substance decays to 180 grams in 9 years.\r
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Algebra.Com's Answer #495234 by ewatrrr(24785) $\"\"$ $\"About$

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document.write( "Hi,
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document.write( "Find the half-life of a radioactive substance 
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document.write( "if 240 grams of the substance decays to 180 grams in 9 years.
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document.write( "The Idea is to 'personalize'  by finding the 'k' value
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document.write( "according to the information given.
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document.write( "180/240 = e^-kt
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document.write( " .75 = e^-9k
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document.write( " ln(.75)/-9 =  k  = .0320
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document.write( " Find the half-life of this radioactive substance: 
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document.write( "  
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document.write( "  ln(.5)/-.0320 = t = 21.66 yrs \n" );
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