Radioactive radium has a half-life of approximately 1599 years. What percent of a given amount remains after 100 years?

Formula: y=Ce^(kt) where y is the amount of radioactive radium at time t, k is the decay constant, and C is the initial amount of radium
1/2C=Ce^(k*1599)
1/2=e^(k*1599)
ln(1/2)=1599klne
ln(1/2)=1599k
ln(1/2)/1599=k
k=-4.3349x10^-4
 
y=Ce^(kt)
y=Ce^[(-4.3349x10^-4)(100)]
y=.9576C
 
Final Answer: 95.76% of radioactive radium is left after 100 years.