To find the unit rate of apartments per floor, you can divide the total number of apartments by the total number of floors.
So, you calculate:
\[ \text{Apartments per floor} = \frac{\text{Total Apartments}}{\text{Total Floors}} = \frac{50 \text{ apartments}}{10 \text{ floors}} = 5 \text{ apartments per floor} \]
Thus, the unit rate is 5 apartments per floor.