document.write( "Question 1180948: 3. A sample of a radioactive isotope was found to be 40 mg 18 days ago and 5 mg today.\r
\n" ); document.write( "\n" ); document.write( "a) What is the half-life of the substance?\r
\n" ); document.write( "\n" ); document.write( "b) How many milligrams of the substance will be left 12 days from today?
\n" ); document.write( " \n" ); document.write( "

Algebra.Com's Answer #810762 by ikleyn(52790) $\"\"$ $\"About$

You can put this solution on YOUR website!
.
\n" ); document.write( "3. A sample of a radioactive isotope was found to be 40 mg 18 days ago and 5 mg today.
\n" ); document.write( "a) What is the half-life of the substance?
\n" ); document.write( "b) How many milligrams of the substance will be left 12 days from today?
\n" ); document.write( "~~~~~~~~~~~~~~~~~\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "

\r\n" );
document.write( "(a)  The ratio of the current mass to the initial mass is   =  = .\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "     It means that 3 (three) half-lives passed from the beginning to the current moment.\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "     It means that 18 days comprize 3 half-lives.  Hence, one half-life is  = 6 days.     ANSWER\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "(b)  12 days from today comprise  12/6 = 2 half-lives;\r\n" );
document.write( "\r\n" );
document.write( "     So, in 12 days after today, the remaining mass will be   =  = 1.25 milligrams.    ANSWER\r\n" );
document.write( "

\r
\n" ); document.write( "\n" ); document.write( "Solved.     //     All questions are answered.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "-------------------\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "On radioactive decay, see the lesson\r
\n" ); document.write( "\n" ); document.write( "    - Radioactive decay problems \r
\n" ); document.write( "\n" ); document.write( "in this site.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "You will find many similar (and different) solved problems there.\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "        Use this lesson as your handbook, textbook, guide, tutorials, and (free of charge) home teacher.\r
\n" ); document.write( "\n" ); document.write( "        Learn the subject from there once and for all.\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Also, you have this free of charge online textbook in ALGEBRA-I in this site\r
\n" ); document.write( "\n" ); document.write( "    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "The referred lesson is the part of this online textbook under the topic \"Logarithms\".\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Save the link to this online textbook together with its description\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Free of charge online textbook in ALGEBRA-I
\n" ); document.write( "https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "to your archive and use it when it is needed.\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

\n" );