The isotope known as carbon-14 is radioactive and will decay into the stable form nitrogen-14. As long as an organism is alive, it ingests air, and the level of carbon-14 in the organism remains the same. When it dies, it no longer absorbs carbon-14 from the air, and the carbon-14 in the organism decays. The half-life of carbon-14 is 5770 years. Assume an organic sample is 18,000 years old.

How many half-lives is 18,000 years? (Round your answer to two decimal places.)
half-lives