We'll use these numbers to mathematically model the "decay" of the class' M&M's®.
In this case, R0 is the initial rate of decays per second at t = 0. The decay constant λ for a statistically large sample is the probability that a given single M&M® will decay in a given time interval.
Each time interval on the clock displayed here is one half-life for the radioactive atoms to decay into a daughter atom (light gray squares). After one half-life, one-half of the original radioactive atoms remain; after two half-lives, one-quarter of the original radioactive atoms remain; so after three half-lives, one-eighth of the radioactive atoms remain. The key to determining the radioactive age of this substance is to assume that it started out with radioactive atoms with no daughter atoms (disregarding the amount of inert material), so the greater proportion of daughter atoms to radioactive atoms corresponds to an older sample.
Note that after a molten sample solidifies, it will start anew with having radioactive atoms with no daughter atoms. So, melting a sample "resets" its solidification age--how long ago has it been since the sample started with radioactive atoms with no daughter atoms.