Question 1140477
N=Noe^(-kt)
half-life is where N=1/2 No so N/No=1/2
ln (1/2)=-kt, since ln e^-kt is -kt
-0.693=-kt, but don't round yet.
t=30.5 in this instance
so 0.693=30.5 k
k=0.022726
A(t)=Aoe^-0.022726t