Final answer:
Keiko had 20 1/4 cup portions of milk.
Step-by-step explanation:
To find the number of 1/4 cup portions Keiko had, we can divide the total number of cups of milk by 1/4. Since Keiko had 5 cups, when we divide by 1/4, we can think of it as multiplying by the reciprocal, which is 4/1. Multiplying 5 by 4/1 gives us:
5 * 4/1 = 20/1 = 20
So Keiko had 20 1/4 cup portions of milk.