Question

How many half-lives have passed in a sample that originally contained 5000 parent isotopes but now has only 625?

Answer 1

3 half lives

Step-by-step explanation:

5000 * (1/2)^n = 625 where n = number of half lives

log ( 625/5000) / log(1/2) = n = 3

5000 2500 1250 625