The half-life of a radioactive material is 3175 years. If there is 400 grams of the radioactive material today, when would there be 25 grams still radioactive?
25 =400 x 1/2^(y/3175), solve for y
0.0625 = 1/2^(y/3175)
y =12,700 Years - when 400 grams decays to 25 grams.
