Plutonium,

239Pu, has a half-life of 24,100 years. What percent of a given amount remains after 100,000 years?

Is this done correctly?

$\displaystyle 1/24100ln(1/2)$

k=0.00002876

$\displaystyle e^(0.00002876(100000))$

= 56.35% after 100,000 years