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Pyschology

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chin:
My kid is taking psychology class in CU, and told me two small questions asked in the class.

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1. You have 4 cards in front of you. You know each card should have an alphabet on one side, and a number of the other side.

The rule is that if the alphabet is a vowel (a, e, i, o, u) the number on the other side should be an even number.

Now the 4 cards in front of you showing "A", "K", "4", "7". The question is which two cards to turn to check if the rule above is being observed.

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2. In the bar, anyone under 18 is not allowed to drink alcoholic drinks. Now 4 young people a, b, c, d stepped into the bar.
- a ordered soda
- b ordered beer
- c is 16 and ordered something
- d is 19 and also ordered something
The question is, which 2 kids to check their id and drinks, to see if the drinking rule is following.

q:

--- Quote from: chin on 05 May 2011, 16:34:50 ---My kid is taking psychology class in CU, and told me two small questions asked in the class.

---
1. You have 4 cards in front of you. You know each card should have an alphabet on one side, and a number of the other side.

The rule is that if the alphabet is a vowel (a, e, i, o, u) the number on the other side should be an even number.

Now the 4 cards in front of you showing "A", "K", "4", "7". The question is which two cards to turn to check if the rule above is being observed.

--- End quote ---

My attempt at answering question 1.

a,e,i,o,u (i.e. the vowels) are a subset of the alphabet such that these letters are paired with an even number.  There is no such condition on the other letters in the alphabet.

Assuming that the original statement is true (i.e. each card has a letter on one side and a number opposite) then two cards that I would choose to turn are
the "A" card and the "7" card. I'd turn these cards to look for contradictory evidence, i.e. if the number opposing "A" is odd, or the letter opposing "7" is a vowel.

chin:
Yes. The checks are correct.

Interestingly I asked the same question on the tea forum. Just over half of the people get the 1st question wrong. The most common mistake is to assume even numbers must be vowels too.

hangchoi:
I think the trick of both questions is that the rule sets up a logic of one direction only but most of them think that the condition can be reversed.

I recalled our first class in Form 6 which taught about the different between 'imply' and 'equivalent'.  ;D "A" implies "B" does not mean that "B" implies "A".

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