Past exam of the particle and nuclear physics course of the University of Cambridge / 2013 / Paper 1 / 1 / c / Solution

For a pure sample, $N=(1000/239)N_A=2.520\times 10^{24}$ nuclei. radioactive activity is $\mathcal{A}=\lambda N$ with $\lambda =\ln 2/t_{1/2}$. Using a year of 365.25 days,The mass number supplies the approximate molar mass in grams per mole. This is initial parent activity; no daughter activity or isotope mixture has been assumed.