Roxanne spent a week at the beach and recorded the number of shells she found each day. According to the table, what was the rate of change between Wednesday and Thursday?
Day | Number of shells
Tuesday | 6
Wednesday | 4
Thursday | 2
Friday | 5
Saturday | 0
Plug the numbers into the formula for rate of change and simplify.
Rate of change
 = \frac{change in value}{change in time}
 = \frac{2 shells - 4 shells}{1 day}
 = \frac{-2 shells}{1 day}
 = -2 shells per day
The rate of change between Wednesday and Thursday was - 2 shells per day.