SSC CGL Preparation – Day 8

Reasoning: Syllogism

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📘 What is a Syllogism?

A syllogism is a form of logical reasoning where conclusions are drawn from two or more given statements (premises). The task is to determine which conclusions logically follow from the given statements.

Syllogisms test your deductive reasoning skills, which are crucial in competitive exams like SSC CGL.

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🧩 Types of Statements in Syllogism

1. Universal Affirmative (A-type)

✅ Example: All A are B.

2. Universal Negative (E-type)

🚫 Example: No A is B.

3. Particular Affirmative (I-type)

☑️ Example: Some A are B.

4. Particular Negative (O-type)

❌ Example: Some A are not B.

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🔄 Important Rules of Syllogism

Premise 1	Premise 2	Valid Conclusion
All A are B	All B are C	All A are C ✅
All A are B	Some B are C	No definite conclusion ❌
Some A are B	Some B are C	No definite conclusion ❌
No A is B	All B are C	No A is C ✅
All A are B	No B is C	No A is C ✅

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🧠 Venn Diagram Approach

To solve syllogisms accurately:

• Draw Venn diagrams for the statements.
• Use elimination and intersection logic to determine valid conclusions.
• Always check all possibilities before confirming.

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📝 Standard Conclusions

Statement Type	Converse is Valid?	Example
All A are B	❌	All apples are fruits ≠ All fruits are apples
Some A are B	✅	Some boys are students ⇒ Some students are boys
No A is B	✅	No dogs are cats ⇒ No cats are dogs
Some A are not B	❌	Not interchangeable

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🚫 Common Mistakes to Avoid

1. Assuming converse of “All A are B” is true (It’s not).
2. Making conclusions from unrelated terms.
3. Missing hidden assumptions.
4. Overlapping diagrams incorrectly.

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🧪 Solved Examples

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🔹 Example 1:

Statements:

1. All dogs are animals.
2. All animals are living beings.

Conclusion:
I. All dogs are living beings.
II. Some living beings are dogs.

✅ Answer: Both I and II follow.

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🔹 Example 2:

Statements:

1. Some pens are pencils.
2. Some pencils are erasers.

Conclusion:
I. Some pens are erasers.
II. All pens are erasers.

❌ Answer: Neither I nor II follow.

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🔹 Example 3:

Statements:

1. All roses are flowers.
2. Some flowers are red.

Conclusion:
I. Some roses are red.
II. All red things are flowers.

❌ Answer: Neither follows.

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🧰 Shortcut Tips for SSC CGL

• For “All A are B” + “All B are C” ⇒ All A are C
• “All A are B” + “No B is C” ⇒ No A is C
• “Some A are B” + “All B are C” ⇒ No definite conclusion
• Memorize the “A-E-I-O” chart and their valid conclusions

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🔍 Practice Strategy

• Practice 10–15 questions per day with time limits.
• Use elimination techniques on tricky options.
• Verify every conclusion using Venn diagrams if confused.