Respuesta :

initial mass No = 30g, mass at half life (N) = 1/2 *30 = 15, so we have

15 = 30 e^-0.1253t

e^-0.1253t = 0.5

-0.1253t = ln 0.5

t = ln 0.5 / -0.1253

t =  5.5 days  to nearest tenth. Answer