To find the rate of snow accumulation, you simply divide the total amount of snow by the total number of days.
Total snow: 90 inches
Total days: 9 days
Rate:
\[ \text{Rate} = \frac{\text{Total snow}}{\text{Total days}} = \frac{90 \text{ inches}}{9 \text{ days}} = 10 \text{ inches/day} \]
So the rate of snow is 10 inches per day.
The unit rate, which is the same in this case because we are already simplifying to a per-day basis, remains:
Unit Rate: 10 inches per day.