What percentage of carbon – 14 ( t_1/2 = 5715 years) remains in a sample estimated to be 18,315 years old? 

The accompanying graph illustrates the decay of ^{88}_{42}Mo, which decays via positron emission. What is the half-life of the decay?

The half-life for the radioactive decay of C-14 is 5715 years and is independent of the initial concentration. How long does it take for 30.00% of the C-14 atoms in a sample of C-14 to decay?

The half-life of Strontium-85 is 65 days. How much of an 80 mg sample is left after 260 days?

Fluorine-18 undergoes positron emission with a half-life of 1.10 x 10^2 minutes. If a patient is given a 250 mg dose for a PET scan, how long will it take for the amount of fluorine-18 to drop to 75 mg?(a) 56 minutes(b) 96 minutes (c) 132 minutes (d) 191 minutes

In a cave in Oregon, archaeologists found bones, plant remains, and fossilized feces. DNA remaining in the feces indi-cates their human origin but not their age. To date the remains, the decay rate was measured and found to be 2.71 disinte-grations/min per gram of carbon. Currently living organisms have a decay rate of 15.3 disintegrations/min per gram of carbon, and the half-life of 14C is 5715 years. How old are the remains? (a) 1460 years(b) 9900 years(c) 14300 years(d) 18600 years