Suppose the chocolate-flavored sugar is A, the fruit-flavored sugar is B, and the two milk-flavored sugars are C 1 and C2 respectively;
So, now nicknames come up with two kinds of candy, one of which is known to be milk-flavored, so at least one of these two kinds of candy must be milk-flavored, that is, one or both of them are milk-flavored.
If only one is milky, then if the milky one is C 1, then the other one has two possibilities, A or B;
If the taste of milk is C2, there are only two possibilities, A or B, because there is only one taste of milk.
Another example is obviously C 1 and C2.
That is, when it is known that at least one smells like milk, there are five possibilities: a, C 1.
b,c 1;
One, C2;
C2
C2 c 1
So the probability that both tastes like milk is 1/5.
This problem is a typical conditional probability problem. When you go to college, you will learn the method of conditional probability in probability theory and answer this conditional probability question in a more formulaic way.