Answer:
If Mia wants to use 6 cups of rice, she would need to multiply the amount of each ingredient by 3, because the original 2 cups times 3 is the 6 cups she wants to use. So the new amount for the recipe would be this:
6 cups of rice
12 cups of milk
1 cup of sugar
3 handful of raisins
3 cinnamon sticks
When asking how many this will serve, we also multiply by 3 the original amount of people which is 4 to get 12 servings of Arroz con leche
The constant of proportionality is the ratio between two directly proportional quantities. Two quantities are directly proportional when they increase and decrease at the same rate. The constant of proportionality k is given by k=y/x where y and x are two quantities that are directly proportional to each other.