Question 812496
Basic General Model, {{{A=Ao*e^(kt)}}}
{{{ln(A)=ln(Ao)+kt*ln(e)}}}
{{{ln(A)=ln(Ao)+kt}}}
{{{k=(ln(A)-ln(Ao))/t}}}
{{{k=(ln(1/2)-ln(1))/1690}}}
{{{highlight(k=-0.000952)}}}


{{{A=60*e^(-0.000952*t)}}}
{{{A=60*e^(-0.000952*670)}}}
{{{highlight(A=32)}}}, close to 31.7 grams.... This is a mistake...


CHECK:
{{{1/2=1*e^(kt)}}}
{{{ln(0.5)=kt*ln(e)}}}
{{{kt=ln(0.5)}}}
{{{k=(1/1690)ln(0.5)=-0.0004101}}}  as the constant k.  Believing this to be a more correct value, you should find {{{A=60*e^(-0.0004101*670)}}}
{{{highlight(A=45)}}}, close to 45.4 grams.  The work shown above "CHECK:" contains a mistake.