Question 953715
General Model, {{{y=p*e^(-kt)}}}


{{{ln(y)=ln(p)-kt}}}, skipping over a step;
{{{-kt=ln(y)-ln(p)}}}
{{{kt=ln(p)-ln(y)}}}
Take two separate directions from that step:


{{{k=ln(p/y)/t}}}  and  {{{t=ln(p/y)/k}}}.  


The half-life data will give you k;
the decay situation data will give you y using the general model formula.



(Sometimes students want to be able to calculate half-life using other given data, so that is why the formula for t).