The question is incorrect, the correct question is;
Carbon-14, which is present in all living tissue, radioactively decays via a first-order process. A one-gram sample of wood taken from a living tree gives a rate for carbon-14 decay of 13.6 counts per minute. If the half-life for carbon-14 is 5720 years, how old is a wood sample that gives a rate for carbon-14 decay of 11.9 counts per minute?
Answer:
C. 1.1 x 103 yr
Step-by-step explanation:
A = count rate of the wood sample
Ao= count rate of a living tissue
t1/2= half life of C-14
t = time taken
From;
0.693/t1/2 = 2.303/t log Ao/A
0.693/5720 = 2.303/t log (13.6/11.9)
1.2 * 10^-4 = 2.303/t * 0.05799
1.2 * 10^-4 = 0.1336/t
t = 0.1336/1.2 * 10^-4
t = 1.1 x 103 yr