For a different punch recipe, the equation,s=4c represents the number of cups of

4

Step-by-step explanation:

If two variables are proportional then

   ...(i)

where, k is constant of proportionality.

The given equation is

      ...(ii)

where,

s = number of cups of seltzer.

c = cups of cranberry juice.

On comparing (i) and (ii), we get

Independent variable:

Dependent variable:

Constant of proportionality:

Therefore, the constant of proportionality is 4.

Givens

So, if she expects 18 guets, and she wants to give 2 pieces to each of them, that means she needs 36 cake pieces.

If each piece is 2 inches long, that means the area per piece is 4 square inches.

Therefore, she needs 144 square inches of cake to give 2 pieces to each guest and have 18 guests.

In terms of length, it would be 72 inches.