1)Suppose that you start with 2.52×1018 radioactive nuclei and 2.09 h later determine that only 8.14E17 nuclei of the substance remains. What is the half-life of this substance?
2)Consider a sample containing 3.91×1019 23892U nuclei. The half-life of 23892U is 4.47 billion years. How many of these nuclei will decay during a 1.727 s interval?