Question

cobalt-60 has a half-life of 5.26 years, how much of a 500 gram sample will be left after 21 years

Answer 1

500*'(1/2)^(21/5.26) grams

Answer 2

You have 14,000 atoms of radioisotope x, which has a half life of 1000 years how much of radioisotope x is after 9000 years ?