To find the rate of change of the purchase price of broccoli in dollars per pound between the points (3, 8.25) and (6, 16.50), we can use the formula for the slope of a line, which is given by:
\[ \text{slope} = \frac{y_2 - y_1}{x_2 - x_1} \]
Here, (x₁, y₁) = (3, 8.25) and (x₂, y₂) = (6, 16.50).
Now, substituting the values:
\[ \text{slope} = \frac{16.50 - 8.25}{6 - 3} \] \[ = \frac{8.25}{3} \] \[ = 2.75 \]
Thus, the rate of change in the purchase price is:
\[ \text{$} 2.75 \text{ per pound} \]
So the answer is $2.75 per pound.