1. The problem statement, all variables and given/known data The decay constant of xenon-142 is 0.462(s^-1), and the decay constant of strontium-90 is 7.85*10^-10 (s^-1). Initially, a sample of radioactive waste material contains equal numbers of strontium-90 and xenon-142 nuclei. Calculate the time taken for the ratio: number of strontium-90 nuclei/number of xenon-142 nuclei to become equal to 1.20*10^6. 2. Relevant equations Not sure 3. The attempt at a solution Not sure, please help!