The half life of C14 is 5730 years. I have a sample that I dug up from a sea cucumber fossil. I expected. 00015ppm of C14 in my living sample, but instead I found that there was exactly1/8th of the expected ratio. How old is my specimen

The answer is 17190 years

Explanation:

Original amount was 5730. To become 1/8 of the original amount, three (3) half life periods will demand because after first half life the amount will become 1/2 and after second half life, amount become 1/2 again (1/2 x 1/2 = 1/4). Third half life, the amount become half 1/2 again (1/2 x 1/2 x 1/2 = 1/8).

For the 3 half life periods we have original amount x numbers of half life periods = 5730 years x 3 = 17190 years