physicsRadioactivity
posted by Sandhya .
1) The number of radioactive nuclei in a particular sample decreases over a period of 15 days to oneseventeenth the original number. What is the halflife (in days) of these nuclei?
2) What is the activity of a sample of 14C that contains 1.22E+21 nuclei?

1) n(t) = No e^kt
where n is number at t and No is starting number
when t = 15. n/No = 1/17 = .0588
so
.0588 = e^15k
ln .0588 = 15 k
k = 2.833/15 = .18888
so
what is t when n/No = 1/2 ??
.5 = e^.18888 t
ln .5 = .693 = .18888 t
t = 3.67 days half life 
Thanks a lot Damon
Is my answer for the second problem correct?