Question

The half-life of Potassium-15 is 1,250 years

(decays continuously). A specimen currently
contains 36 milligrams of Potassium-15. How long
will it take for the specimen to decay to only 15
milligrams of Potassium-15?

Answer 1

Half life = 1250 years
Start amount = 36
End amount = 15
Time = ?

15 = 36 * (1/2)^(x/1250)
0.417 = (1/2)^(x/1250)
ln(0.417) = x/1250 * ln(1/2)
x = 1577.95 years