Question

How much of a radioactive kind of cadmium will be left after 28 years if you start with 982,168 grams and the half-life is 14 years?

Answer 1

Use the decay formula N(t) = N0*(1/2)^(t/half-life).

Here N0 = 982,168 g, t = 28 yr, half-life = 14 yr, so exponent = 28/14 = 2.

N = 982,168*(1/2)^2 = 982,168*(1/4) = 245,542 grams.