Calculas
posted by Cratch .
In the early 1960s, radioactive strontium90 was released during atmospheric testing of nuclear weapons and got into the bones of people alive at the time. If the halflife of strontium90 is 32 years, what fraction of the strontium90 absorbed in 1965 remained in people's bones in 1996?

1996 is 31 years after 1965. Since the half life is 32 years, the amount of Sr90 is nearly, but not quite, reduced by half.
Fot the exact number,
N/No = 2^(31/32) = 0.511