Question 944816
This drug decays to 90% each hour.


General Decay Model,{{{y=Ie^(-kt)}}}
I, initial amount for any t=0.


{{{0.9=1*e^(-k*1)}}}, let's get the k value fast.
{{{ln(0.9)=-k*1}}}
{{{k=-ln(0.9)}}}
{{{k=0.105}}}



How much time to go from 300 mg to 63 mg of this drug?
{{{300*e^(-0.105*t)=63}}}
{{{ln(300)-0.105t=ln(63)}}}
{{{-0.105t=ln(63)-ln(300)}}}

{{{t=(ln(300)-ln(63))/(0.105)}}}


t=14.8 hours