posted by Cratch .
In the early 1960s, radioactive strontium-90 was released during atmospheric testing of nuclear weapons and got into the bones of people alive at the time. If the half-life of strontium-90 is 32 years, what fraction of the strontium-90 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 Sr-90 is nearly, but not quite, reduced by half.
Fot the exact number,
N/No = 2^(-31/32) = 0.511