document.write( "Question 1162733: The half-life of a radioactive element is 5 days. How long will it a 1000 g sample to decay to 62.5 g?\r
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\n" ); document.write( "15 days\r
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\n" ); document.write( "20 days\r
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\n" ); document.write( "2.5 days\r
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\n" ); document.write( "5 days
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Algebra.Com's Answer #786571 by ikleyn(52835) $\"\"$ $\"About$

You can put this solution on YOUR website!
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document.write( "     = 500 g  after 5 days  (one half-life period);\r\n" );
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document.write( "     = 250 g  after 10 days  (two half-life periods);\r\n" );
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document.write( "     = 125 g after 15 days    (three half-life periods);\r\n" );
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document.write( "     = 62.5 g after 20 days   (four half-life periods).\r\n" );
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document.write( "ANSWER.  20 days, or 4 (four) half-life periods.\r\n" );
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\n" ); document.write( "\n" ); document.write( "From my post, you see that the answer can be obtained MENTALLY.\r
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\n" ); document.write( "\n" ); document.write( "See the lesson\r
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