Whats the best way to calculate half life's??
example: Iodine-131 has a half life of 8 days what fraction is left after 20 days?
ie half of it goes away after 8 days.
Therefore, after 20 days, the iodine-131 isotope would have gone through 20/8 = 2.5 half life decomposition processes.
Fraction left over = 1/(0.5)
2.5 = uh.. don't have a calculator
General formula = (0.5)
days/half life length