the isotope has a very short life of 13 half-life days.

Question

estimate the percentage of the original amount of the isotope released by the explosion that remains 3 days after the explosion?

Answer 1

after t days, the amount left is

(1/2)^(t/13)

So, after 3 days, the amount left is

(1/2)^(3/13) = .852 = 85.2%