document.write( "Question 566146: The half-life of 234U, uranium-234x10to the 5th power year. If 98.1% of the uranium in the original sample is present, what length of time(to the nearest thousand years has elapsed? \n" ); document.write( "

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The half-life of 234U, uranium-234x10to the 5th power year.
\n" ); document.write( " If 98.1% of the uranium in the original sample is present, what length of time(to the nearest thousand years has elapsed?
\n" ); document.write( ":
\n" ); document.write( "The radioactive decay formula: A = Ao*2^(-t/h)
\n" ); document.write( "where:
\n" ); document.write( "A = resulting amt after t yrs
\n" ); document.write( "Ao = initial amt
\n" ); document.write( "h = half-life of substance
\n" ); document.write( "t = time
\n" ); document.write( ":
\n" ); document.write( "Using the half-life value of 2.44(10^5) yrs, initial amt as 1
\n" ); document.write( "1*2^(-t/2.44(10^5)) = .981
\n" ); document.write( "using nat logs
\n" ); document.write( " $\"-t%2F%282.44%2810%5E5%29%29\"$ *.693 = -.0192
\n" ); document.write( ":
\n" ); document.write( " $\"-t%2F%282.44%2810%5E5%29%29\"$ = $\"%28-.0192%29%2F.693\"$
\n" ); document.write( "t = -2.44(10^5) * -.027675
\n" ); document.write( ":
\n" ); document.write( "t = +6753 ~ 7,000 yrs \n" ); document.write( "

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