The rubidium-strontium isotopic dating method has been used extensively for approximate age determination of igneous rocks. Yet, this method suffers from unproven assumptions concerning the original concentrations of isotopes in the rocks. The isochron method appears to overcome this weakness. Nevertheless, the isochron method is not the only possible explanation of the isotopic data, and it is clearly invalid in many cases. Another concept, the mixing model, has been introduced which appears to be a valid explanation for a large portion of the isotopic data. It might be considered, therefore, to be a superior scientific model. This report describes a method to demonstrate the apparent superiority of the mixing model over the isochron method to students interested in geochronology.