Assume each card has a beverage on one side, and the drinker's age on the other.
Rule: if someone drinks beer, then (s)he is 21 or older.
You can see four cards (one side of each):
|
beer
|
diet coke
|
23 years old
|
19 years old
|
|
Card #1
|
Card #2
|
Card #3
|
Card #4
|
In order to check whether the rule is true of these cards, which cards do you need to turn over?