The decay of a radioactive substance is modelled using the formula N=1000e−ktN = 1000e^{-kt}N=1000e−kt where N N\,N is the number of atoms after t t\,t years and k k\,k is a positive constant.
Write down the number of atoms when the substance started to decay.
Given that it takes 14.4 years for half of the substance to decay, find the value of k k\,k to 3 significant figures.
Calculate the number of atoms left when t=30t = 30t=30.