Classical Logic Problem 5, Classical Logic Problem

C stole the apple, and what D said was true. The analysis is as follows:

1. If A is true, then B has eaten the apple, and what C said has become true, which violates the conditions, indicating that the hypothesis is not valid.

2. If B is true, then D has eaten the apple, and what C said becomes true, violating the condition, indicating that the hypothesis is not valid.

3. If C is true, then A really means: not B ate the apple; bWhat it really means: It is not dd that eats the apple; What d really means: b is not lying, it is d who ate the apple. At this time, the contradiction between B and D is not true.

4. If D is true, then A really means: not B ate the apple; bWhat it really means: It is not dd that eats the apple; C really means:

I ate the apple myself; What d said was true, and then b lied, confirming that it was not d who ate the apple. So the logic is correct and the assumption is true.

If what A says is true, then B stole the apple.

What the three BCD said is false, so what the three of them say can be obtained:

It was not d that he ate, but that he cate, and that b did not lie.

It's contradictory, it's not true.

If what B says is true, then the apple is eaten by D, the same:

It wasn't B who stole the apple, C ate it, and B didn't lie.

Contradictory, not established.

If what C says is true, then the apple is not eaten by C, and it has to be:

It wasn't what B ate, it wasn't what D ate, and what B didn't lie about was true.

Contradictory, not established.

If what D says is true, then B is lying, and the apple is not eaten by D.

Spoken by the other three can be obtained:

B did not eat the apple, and the apple was not eaten by D, but eaten by C.

There is no contradiction, the assumption is true.

So the one who stole the apple is c

Upstairs .........This is obviously a composite proposition. Namely.

In a mature system of economic policymaking and economics education, economic theory must be more realistic. "In a mature system of economic policy-making and economics education, economic policy must also be based on theoretical logic." ”

Its negative proposition is:

In a mature system of economic policymaking and economics education, economic theory does not have to be more practical. Or, "In a mature system of economic policymaking and economics education, economic policy does not have to be based on theoretical logic." ”

That is. "In a mature system of economic policymaking and economics education, either economic theory does not have to be more realistic, or economic policy does not have to be based on theoretical logic. ”

In particular, it is important to note that the negative proposition of "and" is "or", and "or" cannot be used, because "or" in logic means an incompatible proposition.

The original proposition is equivalent to the inverse negative proposition, i.e., the original proposition is correct, and the inverse proposition is also correct.

Divide the above sentence into 2 propositions:

1.Economic theory must be more realistic.

2.Economic policy must also be based on theoretical logic.

Derive the inverse negative proposition:

1.It is not necessary to use economic theory in the face of reality.

2.Economic policy must not be based on theory and logic.

1. It is easy to know that B's words must be wrong, otherwise C and B will be right at the same time, so the full score of C must not be mathematics;

1) If the full score in the C test is English, only what A says is correct, and A has a full score in Chinese. I don't know if the full score in the B test is English or mathematics;

2) If the full score in the C test is Chinese, then the full score of A and B is unknown.

Is there anything else? ）

2. First of all, A and C have neither English nor Chinese classes, so D has Chinese classes on the fourth floor;

Secondly, B can only take English classes on the third floor, because there are people on the other floors;

I don't know the subjects of A and C (who goes to physics and who goes to mathematics).