Question

A sample is dated using uranium-235 (half-life 704,000,000 years) and it has 4 of the original amount of uranium. How old is the sample?

Answer 1

`1,408,000,000` or `1.408*10^9` years

Explanation:

note: it is impossible to have a value higher than 1 times the original amount if the sample is dated back, so i'm going to assume that you meant `1/4`.

using this:

`1/4 = 1/2 * 2`

meaning `2` half-lives have passed.

`2` * half-life of uranium `= 2* 704,000,000`

`=1,408,000,000` years or `1.408*10^9` years, in standard form.