Question 857664
Stating the time units for the half-life would be a good thing to do.


A quantity, I, of the substance drops to I/2 in 27 times units:
{{{1/2=1*e^(k*27)}}}---simply plugged-in the values about the half life...
{{{ln(1/2)=ln(e^(k*27))}}}
{{{27*k*ln(e)=ln(1/2)}}}
{{{k=(1/27)ln(1/2)}}}
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The value in decimalized form for k is {{{highlight_green(-0.02567)}}}.


Now your question is, {{{t=what}}} for {{{A=0.88*A[o]}}} ?
{{{highlight(0.88=1*e^(-0.02567*t))}}}
...
..
!