To find the constant of proportionality (k) between the total weight and the number of eggs, you can use the formula:
\[ k = \frac{\text{Total Weight}}{\text{Number of Eggs}} \]
In this case, the total weight of 6 eggs is 252 grams.
So, the calculation will be:
\[ k = \frac{252 \text{ g}}{6 \text{ eggs}} = 42 \text{ g per egg} \]
Thus, the constant of proportionality is 42 grams per egg.