Question

Radioactive isotopes can be used to find the age of rocks, fossils, or other artifacts. Carbon-14 has a half-life of 5,730 years. Suppose a sample of charcoal from a primitive fire pit contains one eighth of its original amount of carbon-14. How old is the sample?

Answer 1

Here are 2 hints:

"half-life of 5,730 years" means that every time 5730 years pass by, the amount is cut in half.

1/8 = (1/2)*(1/2)*(1/2)
This shows if 1/8 of the amount is left, then three half-lives have occurred.