Given:
Initial mass = 18 g
k-value = 0.1226
The mass at time t (days) is
[tex]m(t)=18e^{-0.1226t}[/tex]
At half life, m = 18/2 = 9 g.
The time for half life is given by
[tex]9 = 18e^{-0.1226t}[/tex]
Therefore
ln(1/2) = -0.1226t
Hence obtain
t = ln(1/2) / -0.1226
= 5.654 days
Answer: 5.7 days (nearest tenth)
