The decay constant of plutonium-239, a waste product from nuclear reactors, is 2.88×10−5year−1. part a what is the half-life of 239pu?

24100 years
   You can easily convert from decay constant to half-life by using the relationship:
 H = ln(2)/D
  where
 H = half life
  D = decay constant
 ln(2) = natural logarithm of 2.
So
 H = ln(2)/D
 H = 0.693147181/2.88x10^-5 1/year
  H = 2.41x10^4 year
 H = 24100 year