Question 1072026
{{{m(t)=cross(15e-0.087t)}}}
{{{m(t)=15e^(-0.087t)}}}------THIS way.


{{{ln(m)=ln(15*e^(-0.087t))}}}
{{{ln(15)-0.087t=ln(m)}}}
{{{-0.087t=ln(m)-ln(15)}}}
{{{0.087t=ln(15)-ln(m)}}}
{{{highlight_green(t=(ln(15/m))/0.087)}}}



m=5, evaluate t.
{{{t=ln(15/5)/0.087}}}
{{{t=ln(3)/0.087}}}
{{{highlight(t=12.6)}}} or about 12 and a half day