Can someone help me figure out the equation I am supposed to use for this problem?\n\nA nuclear power plant produces radioactive plutonium-239, which has a half-life of 24,110 years. Because of its long half-life, plutonium-239 must be disposed of safely. How long does it take 100 grams of radioactive waste from the nuclear power plant to decay to 20 grams? (Round the growth factor to eight decimal numbers. Round your answer to the nearest year.)\n\nI believe that I have the decay rate correct at 2.87493646?? \n\nI know this should be a simple equation after this but I am having a complete mental block.\n\nThanks for any help.