Logic problem

[oktalist]

Everyone screws up their logical reasoning once in a while. It happens a lot here because we're always arguing about things. This here is a great example of a logic problem that seems obvious but is very easy to get wrong. I just came across it today.

You have four cards, each of which has a letter on one side and a number on the other side. Two of the cards have their letter sides facing you and the other two cards have their number sides facing you:

[A] [K] [4] [7]

You are trying to determine whether the following proposition is false: "If a card has a vowel on one side, then it has an even number on the other side." Which two cards should you turn over?

 

[TheOmenCorpse]

A, 7

Frank leaves home. When he tries to return, a man wearing a mask blocks his path.

1.) What is Frank doing?
2.) What is the masked man's occupation?
3.) Where is Frank's "safe place?

 

[Aurgelmir]

A, 7

Frank...

Actually no. You turn over A and 4. You want to prove/disprove that Vowels and even numbers are correlating. The Statement doesn't mention odd numbers consonants, so turning over K or 7 will not yield any information at all.

Turn over A and it is an 8, statement is still true.
Turn over K and it is any number, statement is still true.
Turn over 7 and it is a consonant, still true
Turn over 4 and it is a consonant... ding ding ding you proved the statement wrong.

If 4 is a vowel though you do not have enough information to prove the statement false, and it can be considered true until falsified. This is what is known as the falsification principle

PS: your riddle doesn't strike me as a logic problem though It is a good riddle that I can solve though

 

[Rowan93]

A, 7

Frank...

Actually no. You turn over A and 4. You want to prove/disprove that Vowels and even numbers are correlating. The Statement doesn't mention odd numbers consonants, so turning over K or 7 will not yield any information at all.

Turn over A and it is an 8, statement is still true.
Turn over K and it is any number, statement is still true.
Turn over 7 and it is a consonant, still true
Turn over 4 and it is a consonant... ding ding ding you proved the statement wrong.

If 4 is a vowel though you do not have enough information to prove the statement false, and it can be considered true until falsified. This is what is known as the falsification principle

PS: your riddle doesn't strike me as a logic problem though It is a good riddle that I can solve though

If you turn over 7 and it's a vowel, it proves the statement false. If you turn over 4 and it's a consonant, you've proved nothing, because the statement isn't "if and only if", it's simply "if".

 

[Aurgelmir]

A, 7

Frank...

Actually no. You turn over A and 4. You want to prove/disprove that Vowels and even numbers are correlating. The Statement doesn't mention odd numbers consonants, so turning over K or 7 will not yield any information at all.

Turn over A and it is an 8, statement is still true.
Turn over K and it is any number, statement is still true.
Turn over 7 and it is a consonant, still true
Turn over 4 and it is a consonant... ding ding ding you proved the statement wrong.

If 4 is a vowel though you do not have enough information to prove the statement false, and it can be considered true until falsified. This is what is known as the falsification principle

PS: your riddle doesn't strike me as a logic problem though It is a good riddle that I can solve though

If you turn over 7 and it's a vowel, it proves the statement false. If you turn over 4 and it's a consonant, you've proved nothing, because the statement isn't "if and only if", it's simply "if".

Yes, you are in fact correct, and I take back what I said as the original statement never say that a card with an even number has to have a vowel on the other side.
Which means the sentence could be written like this:

"All cards with vowels on them have even numbers, but not all even numbers have vowels." Which is sort of how I started out thinking, but messed my train of thought up a little

OP: Was the choice of A, K, 4 and 7 an accidental choice?

 

[oktalist]

A, 7

Well done, damn you.

Frank leaves home. When he tries to return, a man wearing a mask blocks his path.

1.) What is Frank doing?
2.) What is the masked man's occupation?
3.) Where is Frank's "safe place?

1. Bringing nectar to feed to his her larval sisters.
2. Beekeeper.
3. No idea.

OP: Was the choice of A, K, 4 and 7 an accidental choice?

I'm guessing not, but it wasn't my choice.

I got it wrong the first time I saw it. One automatically thinks A and 4, because the proposition mentions vowels and even numbers.

It gets easier if you change the values on the cards from abstract letters and numbers to more real-life concepts, for example drinks and ages:

[beer] [cola] [22] [16]

If each card represents a person, with their age and the drink they are drinking, then which two cards should you turn over to determine whether the following proposition is false? "If a person is drinking an alcoholic drink, then they are aged 18 or over."