25. The carbon-14 in a carbon sample is decaying at approximately 6.5 atoms per hour per gram of carbon. Determine the approximate age of the sample.
25.
6.5 atoms per hour is one-fourth of 26 atoms per hour, so the sample is two half-lives (of 5730 years each) older than the sample in the text example and Table 23.1 (page 958): years. Using the formula ln gives 40,253 years, which again—given the imprecision of the data of 6.5 atoms per hour—should be rounded to 40,000 years.