Radioactive substances decay by first-order kinetics. How many years would be required for a sample containing strontium-90 to decrease to 58.32% of its initial activity? The half-life of strontium-90 is 2.88e1 years.

Answer 1

k = 0.693/t_1/2
Substitute k into the below.
ln(No/N) = kt
No = 100
N = 58.32
K from above.
Solve for t in years.