Carbon from an ancient tooth was extracted and formed into a sample of benzene. using the information from example 30.11 and its preceding discussion, what is the mass of the carbon, both 12c and 14c, in the sample tested in example 30.110? strategize we can assume that, thousands of years ago, the sample had an initial activity of 54.9 counts per minute- identical to the activity of a modern sample. the present activity is lower due to the decay of the 14c since the death of the mammoth prepare equation 30.16 gives the decrease of the activity a function of time as as ro (1/2)/12. the current activity is r r 11.5 counts per minute, and we assume that the initial activity was ro = 54.9. t is the time since the mammoth died-the age of the skeleton solve we solve for t by rearranging terms and computing a natural logarithm, as in t/t12 ro g) in in t1/2 we then solve for the time t: 5730 yr n in (1/2) r 11.5 1/2 12,900 yr in in (1/2) t = = 54.9