To find the constant of proportionality in the data table for the bakery's flour usage, we can analyze the relationship between the number of loaves and the amount of flour needed.
Given that the recipe calls for 2 cups of flour per loaf of bread, we can create the following pairs based on the number of loaves:
- 1 loaf = 2 cups of flour
- 2 loaves = 4 cups of flour
- 3 loaves = 6 cups of flour
- 4 loaves = 8 cups of flour
This means the relationship can be expressed as:
\[ \text{Flour} = 2 \times \text{Loaves} \]
From the data given, the pairs can be summarized as follows:
- (1, 2)
- (2, 4)
- (3, 6)
- (4, 8)
The constant of proportionality is the coefficient of the number of loaves, which is 2 (i.e., for every loaf, the amount of flour increases by 2 cups).
Therefore, the constant of proportionality ratio appears at the pairs that relate loaves to flour as (1, 2).
Thus, the answer is: \((1, 2)\)