You find the frozen remains of a woolly mammoth in an Alaskan glacier. You analyze a bit of the tusk and find that its ¹⁴C:¹²C ratio is about one-fourth (25%)of the baseline level typically found in living organisms. Given that the half-life of ¹⁴C is 5,730 years, when did the mammoth die?
A)5,730 years ago
B)almost 12,000 years ago
C)at least 25,000 years ago
D)approximately 75,000 years ago

Question

Quizplus · Accepted Answer

The fact that the 14C:12C ratio is about 25% of the baseline level suggests that half of the 14C has decayed. Since the half-life of 14C is 5,730 years, we can estimate that it has been twice the half-life since the mammoth's death. 
2 × 5,730 = 11,460 years ago, which is closest to option B (almost 12,000 years ago). Therefore, the best choice is B.

You Find the Frozen Remains of a Woolly Mammoth in an Alaskan