Strontium-90 decays through the emission of beta particles. It has a half-life of 29 years. How long does it take for 80% of a sample of strontium-90 to decay?

Question

Show process of how you got this

Answer 1

k = 0.693/t_1/2
ln(No/N) = kt

Use No = 100
N = 20
k from above
solve for t in years.

Answer 2

27