Karnataka Forest Guard /Reasoning Ability

Syllogism

Logical Reasoning · free study notes · Updated

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Syllogism – Study Notes

(For Karnataka Forest Guard – Reasoning Ability)

1. What is a Syllogism?

A syllogism is a deductive reasoning puzzle that presents a set of statements (premises) and asks you to deduce a conclusion.

  • Premise: A statement that is assumed to be true.
  • Conclusion: A statement that follows logically from the premises.
  • Goal: Find the unique statement that satisfies all given conditions.

2. Key Points to Remember

# Point Why It Matters
1 Understand the structure Usually “X is Y”, “Y is Z”, “X is Z” type.
2 Count the elements Number of people, objects, or positions given in the problem.
3 Identify the “unknown” The variable you need to find (e.g., position of a person).
4 Check consistency No two statements contradict each other.
5 Use elimination Rule out options that violate any premise.
6 Keep a systematic list Write down all possibilities and cross‑check.
7 Watch for “exactly” vs “at least” “Exactly” limits the choice; “at least” only gives a minimum.

3. Types of Syllogisms (Common in Forest Guard Exam)

Type Example Typical Question
1. Linear (One‑Dimension) “A is to the left of B.” Arrange objects in a row.
2. Circular (Ring) “C is opposite D.” Positions on a circle.
3. Vertical/Horizontal “X sits above Y.” Grid or matrix.
4. Relative Position “A is between B and C.” Intermediary placement.
5. Conditional “If A is in the first row, then B is in the third.” Conditional placement.

4. Step‑by‑Step Method

  1. Read the Problem Carefully

    • Highlight all given statements.
    • Note any “exactly”, “only”, “at least”, or “at most” clues.

  2. List All Entities

    • Create a table or diagram with each entity (person, vehicle, etc.).
    • Mark unknown positions with blanks.

  3. Apply Each Premise

    • For each statement, fill in what you know immediately.
    • Use “X is to the left of Y” → X comes before Y in the row.

  4. Cross‑Check

    • After applying a premise, verify that no earlier placement violates a previous statement.

  5. Eliminate Contradictory Options

    • If a placement creates a conflict, backtrack and try the next possibility.

  6. Confirm Uniqueness

    • Ensure that only one arrangement satisfies all premises.

  7. Answer the Question

    • Once the complete arrangement is found, read off the required information.

5. Worked Example

Problem
There are 5 people (A, B, C, D, E) standing in a straight line from left to right.

  1. A is somewhere to the left of B.
  2. C is between A and B.
  3. D is to the right of C.
  4. E is second from the left.
  5. B is not in the last position.

Question: Who stands third from the left?

Step 1 – Set Up

Position 1 2 3 4 5
Person

Step 2 – Apply Premise 4

E is 2nd from the left → Place E at position 2.

Position 1 2 3 4 5
Person E

Step 3 – Apply Premise 1

A is left of B. So A cannot be at position 5, B cannot be at position 1.

Step 4 – Apply Premise 2

C is between A and B.

  • If A is at position 1, B must be at position 3 or 4 (C occupies the middle).
  • If A is at position 3, B must be at position 5 (C at 4).
  • If A is at position 4, B cannot be at 5 because C would need to be between them, impossible.

Step 5 – Apply Premise 3

D is to the right of C. So D cannot be left of C.

Step 6 – Apply Premise 5

B is not last → B ≠ 5.

Try Possibility A = 1

Pos 1 2 3 4 5
P A E C B
  • C is at 3 → satisfies “C between A and B”.
  • D must be right of C → D at 4.
  • Check all premises:
    1. A left of B ✔️
    2. C between A and B ✔️
    3. D right of C ✔️
    4. E second ✔️
    5. B not last ✔️

All premises satisfied!

Answer: The person standing third from the left is C.

6. Quick Revision Summary

Topic Quick Tips
Premises Treat each as a rule that cuts down possibilities.
Positioning Use “left/right”, “between”, “opposite”, “adjacent”, etc.
Elimination If a placement violates any rule, discard it immediately.
Unique Solution The final arrangement must satisfy all statements.
Practice Draw diagrams, write

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