Question Number 116238 by Ar Brandon last updated on 02/Oct/20
$$\mathrm{How}\:\mathrm{long}\:\mathrm{does}\:\mathrm{it}\:\mathrm{take}\:\mathrm{for}\:\mathrm{the}\:\mathrm{disintegration}\:\mathrm{of} \\ $$$$\frac{\mathrm{3}}{\mathrm{10}}\:\mathrm{of}\:\mathrm{an}\:\mathrm{atom}\:\mathrm{with}\:\mathrm{radioactive}\:\mathrm{constant}\:\lambda\:? \\ $$