Tritium, a radioactive isotope of hydrogen, has a half-life of 12.4 years. Of an initial sample of 69 grams, how much will remain after 75 years?

Answer 1

the amount left in t years is

69*(1/2)^(t/12.4)

so, plug in t=75

Note that that's about 6 half-lives.

Answer 2

1.5848

Answer 3

Answer is actually 1.04257