Final answer:
The constant of proportionality between the number of eggs and pancakes is 1.8.
Step-by-step explanation:
The constant of proportionality between the number of eggs and pancakes is found by dividing the number of eggs by the number of pancakes. In this case, since 36 eggs are cooked with 20 pancakes, the constant of proportionality is 36/20 or 1.8. Therefore, the correct answer is A. 1.8.