document.write( "Question 1113185: Another equation used to determine the decrease in mass, M, in milligrams, of a radioactive isotope after t years is $\"+M=100e%5E%28-0.035t%29+\"$ . How many years will it take a substance to degrade from 100 mg to 30 mg? \n" ); document.write( "

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Another equation used to determine the decrease in mass, M, in milligrams, of a radioactive isotope after t years is $\"M+=+100%2Ae%5E%28%28-.035t%29%29\"$ . How many years will it take a substance to degrade from 100 mg to 30 mg?
\n" ); document.write( ":
\n" ); document.write( " $\"100%2Ae%5E%28%28-.035t%29%29+=+30\"$
\n" ); document.write( " $\"e%5E%28%28-.035t%29%29+=+30%2F100\"$
\n" ); document.write( " $\"e%5E%28%28-.035t%29%29+=+.3\"$
\n" ); document.write( " $\"ln%28e%5E%28%28-.035t%29%29%29+=+ln%28.3%29\"$
\n" ); document.write( "log equiv of exponent, find the ln, the ln of e = 1
\n" ); document.write( "-.035t = -1.2034
\n" ); document.write( " $\"t+=+%28-1.2034%29%2F%28-.035%29\"$
\n" ); document.write( "t = 34.4 years
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