Logic, IQ, and Lateral Thinking Problems.

[Auntie Blackbeard]

If Black bart be roight I'll eat me own knittin!

[Roy Hunter]

Nope.

[Calico Jack]

3 and red

ack

[Roy Hunter]

Wrong-o, bird brain!

[Zankou 2.0]

This is unsolvable?

[Roy Hunter]

Are we giving up?

OK, I'll put the solution in tiny letters.

**SPOILER!!**

You turn over the 8 and the brown-backed card. If you turn over the 3 and it has a red back, you don't disprove the proposition; likewise if you turn over the red-backed card and it is an odd number you haven't disproved the proposition. You need to check that the back of the even numbered card is red (there could be other colours), and you need to check that the front of the brown-backed card is not an even number (since there are only odd and even numbers). It's called the Wason selection task. It's actually quite famous.

[daftbeaker]

"The logical proposition is that if a card has an even number on one face, then the back of it is red. You may turn over two cards to test the proposition. Which cards do you turn over?"

Tiny words:
Surely that says nothing about whether or not brown backed cards have odd or even numbers on? Given that the logical proposition is that even numbers have red backs, turning over the 8 would show whether or not that holds true for the 8 and turning over the red backed card would show whether that holds true for that card. Given the limit on the number of cards, if both match the proposition then that would seem to validate it. Turning over the brown card will give information on what is on the face of brown-backed cards but does not seem to give information on a relationship between even numbers and red-backed cards.

Or am I missing something?

[Roy Hunter]

More tininess.

Turning over the 8 would show whether it has a red back (which supports the proposition) or a brown back (which does not support it). Turning over the 3 would show you what colour the back of an odd number card has, which has no bearing on the proposition. Turning over the red backed card would have no bearing on the proposition, since there is no reason for an odd numbered card to not have a red back. Turning over the brown-backed card would show whether it was an even number (which would not support the proposition), or an odd number which has no effect on the proposition. The only tests you want to carry out are the ones which can disprove the proposition, which are turning over the 8 and the brown-backed card.

[daftbeaker]

More tininess.

Turning over the 8 would show whether it has a red back (which supports the proposition) or a brown back (which does not support it). Turning over the 3 would show you what colour the back of an odd number card has, which has no bearing on the proposition. Turning over the red backed card would have no bearing on the proposition, since there is no reason for an odd numbered card to not have a red back. Turning over the brown-backed card would show whether it was an even number (which would not support the proposition), or an odd number which has no effect on the proposition. The only tests you want to carry out are the ones which can disprove the proposition, which are turning over the 8 and the brown-backed card.

So the proposition is that even numbered cards exclusively have red backs? If so then I understand.

[Roy Hunter]

The proposition is that all even numbered cards have red backs. That doesn't exclude the possibility that an odd numbered card has a red back, but it does exclude the possibility that an even numbered card has a brown back. So checking a red-backed card tells you nothing, but checking a brown-backed card does tell you something.

[Zankou 2.0]

D'oh.

[Roy Hunter]

What happens if Pinocchio tells you his nose is going to grow?

[Rainswept]

The Copenhagen interpretation of quantum mechanics teaches that his nose will both grow and not grow simultaneously.

[gronank]

What happens if Pinocchio tells you his nose is going to grow?

I was asked this exact thing yesterday. You don't happen to interact a lot with engineering students from the Gothenburg area, do you?

[Qwertyuiopasd]

What happens if Pinocchio tells you his nose is going to grow?

Also depends on your interpretation of what constitutes a lie. Being an action in the future, he may have no way of knowing what will happen, so it's neither a lie nor a truth. Or actually, that might make it default to a lie, since if he doesn't know, he's saying something he isn't sure is true as if it were true, so it's a lie. His nose would then grow, which would be confusing, but consistent, since he technically lied.