Question 1058423
{{{y=50*e^(-kt)}}}


{{{ln(y)=ln(50)-kt}}}
{{{-kt=ln(y)-ln(50)}}}
{{{kt=ln(50)-ln(y)}}}
{{{k=(1/t)ln(50/y)}}}
Use halflife:
{{{k=(1/3.1)(ln(50/25))}}}
{{{k=ln(2)/3.1}}}
{{{highlight(k=0.22359)}}}


{{{kt=ln(50)-ln(y)}}}
{{{t=(1/k)(ln(50/y))}}}
How long to reach 8 grams?
{{{t=(1/0.22359)ln(50/8)}}}
{{{highlight(t=ln(25/4)/0.22359)}}}