The structures of decagonal quasicrystals have been described as periodic stacks of decagonal quasicrystalline planes. Decagonal covering and Penrose tiling have been used to model the lattice structure of the quasicrystalline plane. We compare quasi-unit-cell models (decagon covering with decorated decagon) to Penrose-tile models (Penrose tiling with decorated rhombus tiles) and show that a quasi-unit-cell model can be interpreted as a Penrose-tile model with inflated rhombus tiles. For any given decagonal quasi-unit-cell model, there is a systematic way to generate the equivalent rhombus decorations of Penrose tiling. In general, the edge of the unit rhombus tiles in an equivalent Penrose decoration is shown to be τ 4 times longer than the edge of the quasi-unit decagon. This equivalence can be used in computing atomic densities of quasi-unit-cell models.