Half Life Question help?

Question

The half-life of carbon-14 is 5730 years. The daughter is stable nitrogen-14. A sample contains 1/4 C-14 and 3/4 N-14. How old is the sample?

Answer 1

Assuming we started with no N-14 when the sample was created, it has gone through 2 half-lives with C-14 disintegeration (2 half-lives means 1/2 x 1/2 or 1/4 remaining). So age = 11460 years give or take a few days.