SOLUTION: The half-life of a radioactive material is the time in which half of it will disintegrate. If its amount after t years is {{{ (5)(2^(-t/90)) }}}, what is its half life?

Algebra ->  Exponential-and-logarithmic-functions -> SOLUTION: The half-life of a radioactive material is the time in which half of it will disintegrate. If its amount after t years is {{{ (5)(2^(-t/90)) }}}, what is its half life?      Log On

Half-life is when   2^(-t/90) = 2^(-1) = .


It is when


     = -1,   or   t = 90.


ANSWER.  In this problem, the half-life is 90 years.