Question

Scientists found a fossilized bone from an organism at an excavation site in North Dakota. When they took the bone back to the lab, they realized that the bone had only 12.5% of the total carbon-14 left. Based on the amount of carbon-14 left in the bone how old is the bone if the half-life of carbon-14 is 5730 years? A) 5730 years old B) 17,190 years old C) 71,625 years old D) Cannot determine answer based on information given.

Answer 1

B. 17190 years old

Step-by-step explanation:

It takes 5730 years for a particular amount of carbon-14 in the bone to reduce by halve its initial quantity. So

At the death of the animal the c-14 content was 100%, the decay steps is shown below

100% decays down to

50% in 5730 yrs.

The 50% decays down to

25% in 5730 yrs.

The 25% decays down to

12.5% in 5730 years.

This means that for 12.5% of c-14 to be left the c-14 has gone through 3 half lives which puts its age at

5730+5730+5730 = 17190 years