1. The problem statement, all variables and given/known data The formula being derived is N=No*e^k*t, from the equation Nn=No/2^n where No is the initial number of particles and the lowercase n in the second equation is the number of half lives. The n in Nn just indicates the number of particles after so many half lives. You might also use the formula for the decay constant so feel free to. 2. Relevant equations N=No*e^kt Nn=No/2^n k=-.693/t 3. The attempt at a solution I haven't really made any meaningful progress so I leave it to you!