Chapter 5. The Ultimate Weapon: Conquering the Highly Difficulty Quiz

Congratulations! You have now covered everything from the basics of logic to the more advanced techniques of reductiometry. In the last class, we will teach you the final algorithm so that you can demonstrate your master’s skills without panicking when you encounter the ‘complex reasoning quiz’ that makes test takers cry in the actual NCS or PSAT.

1. 1% experts’ ‘problem solving algorithm’

The moment you read the question, you have 5 seconds to decide the next 4 steps.

Logic Quiz Defeating Process

1. Symbolization

Simplify all sentences into →, ∧, ∨.

2. Confirmed search

Find information with fixed true/false values, such as ~A and B.

3. Chain connection

If there is confirmed information, the chain is connected. If not, the treatment is taken and combined.

4. Choose a strategy

If the chain is broken, break through with 'reductio' or 'number of cases'.

2. Solving evolving problems (Step 9: The ultimate in complex reasoning)

Problem 6 (NCS/PSAT style): If all five conditions below are true, which conclusion is necessarily true?

If A attends the meeting, B also attends.

B does not attend or Byoung attends.

If Byeong does not attend, Jeong will attend.

If Mu attends, Jeong does not attend.

Person A attended the meeting.

Jeong attended and Eul did not attend.
Both Byeong and Mu attended.
Byeong attended, but Jeong did not.
Eul attended and Mu did not attend.

[Master’s thought flow]

Symbolization:

(1) A → B
(2) ~ ∨ bottle (Conversion: ** → bottle **)
(3) ~ Bottle → Jeong
(4) Mu → ~jeong (Treatment: jeong → ~mu)
(5) A (confirmed information!)

Chain Link:

A (5) → B (1) → B (2)
Now that it is a disease (T), the antecedent is negated in (3) “~byeong → Jeong”, so forward inference is no longer possible.
However, it is possible to connect “mu → ~jeong”, which is the counterpart of (4) “jeong → ~mu”, and “~jeong → bottle”, which is the counterpart of (3).

Find the final conclusion:

Since A attended, B must attend (T)
Since Eul attended Byeong must attend (T)
It is unknown whether Mu will attend (it is unknown what will happen to Jeong even if Mu does not come, based on premise 3)
However, option 4: ** was present and the part ’** is 100% certain.
Mu did not attend? If Mu attends (T), affection will not come (~jeong) due to (4), and illness will come due to the treatment of (3), “~jeong → illness,” which does not contradict the facts already confirmed. However, on the other hand, just because radish did not come does not create a logical contradiction.

Re-analysis of options:

Numbers 1, 2, and 3 require definitive information on either Yes or No, but are unknown.
Wait! Let’s look at (3) and (4) again.
A (T) → Eul (T) → Byeong (T).
If Byeong attends (T), the antecedent (~ Byeong) of (3) becomes false and whether Jeong is present is unknown.
If it is unclear whether it is defined, it is also unclear whether it is meaningless.
But the point of this problem is that ‘Eul attended’ and ‘Byeong attended’ are 100% certain.

Correct answer: Eul and Byeong must attend. (Select the most obvious combination among the options)

3. The final blow to passing: ‘Mistake prevention’ checklist

“Or (∨)” processing: Was it necessarily changed into a conditional statement of “If not A, then B” and inserted into the chain?
“Only in the case of ~”: Did you write the arrow direction in the opposite direction? (A iff B)
“Some” vs “All”: Did you carelessly connect a chain of arrows in the Some proposition?
Time Management: If you don’t see the chain within 1 minute, do you immediately start reductio (what if)?

🎓 Master’s final message: Completion of the 200,000 won lecture roadmap

Studying logic is ‘quality over quantity’. Rather than solving 100 problems mechanically, it is more important to practice completely decomposing 10 problems into the steps of ‘Symbolization - Chain - Confirmation - Inference’.

The reductio law and number of cases learned through this class will be powerful tools that will make your brain the clearest even in complex decision-making situations in life.

We sincerely support your success!

[Appendix: Premium Logic Summary PDF Guide to be downloaded] (This lecture plan has been optimized for practical application.)

Public Enterprise Korean Language Logic Ch5. Final Weapon - Roadmap for conquering and passing di...