A bone contains 12.5% of the carbon-14 it began with. how old is the bone?

First, we need to know the half life of carbon-14, which is approximately 5,717 years.

A half life is how much time it takes for the sample to decay to half of its original amount. So in 5,717 years, a 1 gram sample of carbon-14 would decay to 0.5 grams.

Similarly, if we start with 100% of a sample , we can keep dividing this number by 2 until we reach 12.5% to find out how many half lives passed.

Remember, when the sample is still 100%, 0 half lives have passed.

% remaining: 100 > 50 > 25 > 12.5

Half lives: 0123

3 half lives passed.

Multiply the half life of carbon-14 (5,717 years) by how many half lives passed.

5

,

717

⋅

3

=

17

,

151

Explanation: