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Question

Three statements are given, followed by three conclusions I, II and III. Considering the statements to be true, even if they seem to be at variance from commonly known facts, decide which conclusion(s) logically follows from the statements.

Statement :

All schools are colleges.

All colleges are houses.

All houses are roads.

Conclusion :

I. All schools are roads.

II. All schools are houses.

III. All colleges are roads.

The correct answer is

All conclusions follow.

Analyzing Syllogism Statements

The question provides three statements that describe relationships between different categories: schools, colleges, houses, and roads. In logical reasoning, specifically syllogisms, we assume these statements are true, even if they don't match real-world facts. Our goal is to see what conclusions logically follow from these given truths.

Let's represent the relationships given in the statements:

  • Statement 1: All schools are colleges. This means if something is a school, it must also be a college. We can represent this as Schools → Colleges.
  • Statement 2: All colleges are houses. If something is a college, it must also be a house. We can represent this as Colleges → Houses.
  • Statement 3: All houses are roads. If something is a house, it must also be a road. We can represent this as Houses → Roads.

By combining these statements, we can see a chain of relationships:

Schools $\rightarrow$ Colleges $\rightarrow$ Houses $\rightarrow$ Roads

This chain implies that anything belonging to a category also belongs to all subsequent categories in the chain.

Evaluating Syllogism Conclusions

Now, let's examine each conclusion based on the relationships derived from the statements.

  • Conclusion I: All schools are roads.

    From our derived chain, we have Schools $\rightarrow$ Colleges $\rightarrow$ Houses $\rightarrow$ Roads. This means if something is a school, it is a college, and if it is a college, it is a house, and if it is a house, it is a road. Therefore, if something is a school, it must logically be a road. Conclusion I follows from the statements.

  • Conclusion II: All schools are houses.

    Looking at the chain again: Schools $\rightarrow$ Colleges $\rightarrow$ Houses. This part of the chain shows that if something is a school, it is a college, and if it is a college, it is a house. Thus, if something is a school, it must logically be a house. Conclusion II follows from the statements.

  • Conclusion III: All colleges are roads.

    Consider the part of the chain starting from colleges: Colleges $\rightarrow$ Houses $\rightarrow$ Roads. This shows that if something is a college, it is a house, and if it is a house, it is a road. Therefore, if something is a college, it must logically be a road. Conclusion III follows from the statements.

Summary of Logical Conclusions

Based on the analysis of each conclusion against the given statements and the logical relationships formed, we found that all three conclusions (I, II, and III) logically follow.

We can visualize this with a simple inclusion diagram or consider the set theory representation:

  • Schools $\subseteq$ Colleges
  • Colleges $\subseteq$ Houses
  • Houses $\subseteq$ Roads

From set theory, if A $\subseteq$ B and B $\subseteq$ C, then A $\subseteq$ C. Applying this:

  • Schools $\subseteq$ Colleges and Colleges $\subseteq$ Houses $\implies$ Schools $\subseteq$ Houses (Conclusion II)
  • Colleges $\subseteq$ Houses and Houses $\subseteq$ Roads $\implies$ Colleges $\subseteq$ Roads (Conclusion III)
  • Schools $\subseteq$ Houses and Houses $\subseteq$ Roads $\implies$ Schools $\subseteq$ Roads (Conclusion I)
Statement Relationship
All Schools are Colleges Schools $\subseteq$ Colleges
All Colleges are Houses Colleges $\subseteq$ Houses
All Houses are Roads Houses $\subseteq$ Roads
Conclusion Relationship Logically Follows?
I. All Schools are Roads Schools $\subseteq$ Roads Yes (Schools $\subseteq$ Colleges $\subseteq$ Houses $\subseteq$ Roads)
II. All Schools are Houses Schools $\subseteq$ Houses Yes (Schools $\subseteq$ Colleges $\subseteq$ Houses)
III. All Colleges are Roads Colleges $\subseteq$ Roads Yes (Colleges $\subseteq$ Houses $\subseteq$ Roads)

Since all conclusions I, II, and III are logically derived from the given statements, all conclusions follow.

Revision Table for Syllogism Logic

Concept Explanation
Syllogism A type of logical argument where a conclusion is inferred from two or more statements (premises).
Statements (Premises) The initial assertions given as true.
Conclusion A judgment or decision reached by reasoning. We check if it MUST be true based on the statements.
"All" Statements Indicates complete inclusion of one category within another (e.g., All A are B means A is a subset of B).
Logical Deduction The process of reasoning from one or more general statements (premises) to reach a logically certain conclusion.

Additional Information on Syllogism Solving

Syllogism problems like this one test your ability to follow logical rules. There are different methods to solve them:

  • Chain Method: As used in this solution, link the statements together if they share a common term (e.g., A $\rightarrow$ B, B $\rightarrow$ C implies A $\rightarrow$ C). This works well for 'All' statements forming a clear chain.
  • Venn Diagrams: You can draw overlapping circles to represent the categories and the relationships between them based on the statements. Then, check if the conclusion is necessarily true according to the diagram.
  • Rules of Syllogism: There are formal rules based on the types of statements (Universal Affirmative: All A are B; Universal Negative: No A are B; Particular Affirmative: Some A are B; Particular Negative: Some A are not B) and the distribution of terms.

For 'All A are B', 'A' is the subject and is distributed, 'B' is the predicate and is not distributed. For 'All B are C', 'B' is distributed, 'C' is not. When linking 'All A are B' and 'All B are C', the middle term 'B' must be distributed in at least one premise to draw a valid conclusion about A and C (e.g., All A are C).

In this problem, the middle terms (Colleges in S1 & S2, Houses in S2 & S3) are subjects of 'All' statements, so they are distributed, allowing conclusions to be drawn across them.

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Important Questions from Conventional Syllogism

  1. Read the given statements and conclusions carefully. Assuming that the information given in the statements is true, even if it appears to be at variance with commonly known facts, decide which of the given conclusions logically follow(s) from the statements.

    Statements:

    No bank is an office.

    All offices are stalls.

    Conclusions:

    I. No bank is a stall.

    II. No stall is a bank.

    III. Some stalls are offices.

    IV. All the stalls are offices

  2. Read the given statements and conclusions carefully. Assuming that the information given in the statements is true, even if it appears to be at variance with commonly known facts, decide which of the given conclusions logically follow(s) from the statements.

    Statements:

    All flowers are beautiful.

    Vaidehi is beautiful.

    Conclusions:

    I. Vaidehi is a flower.

    II. Some beautiful are flowers.

  3. Read the given statements and conclusions carefully. Assuming that the information given in the statements is true, even if it appears to be at variance with commonly known facts, decide which of the given conclusions logically follow(s) from the statements.

    Statements:

    1. All rugs are blankets.

    2. All blankets are pillows.

    3. Some blankets are frames.

    Conclusions:

    I. All pillows are rugs.

    II. Some pillows are rugs.

    III. All rugs are frames

  4. Read the given statements and conclusions carefully. Assuming that the information given in the statements is true, even if it appears to be at variance with commonly known facts, decide which of the given conclusions logically follow(s) from the statements.

    Statements:

    Some fingers are toes.

    Some toes are rings.

    Some rings are hands.

    Conclusions:

    I. Some hands are toes.

    II. Some rings are fingers.

    III. Some hands are fingers.

    V. Some fingers are rings.

  5. Read the given statements and conclusions carefully. Assuming that the information given in the statements is true, even if it appears to be at variance with commonly known facts, decide which of the given conclusions logically follow(s) from the statements.

    Statements:

    All polygons are angles.

    All angles are diagonals.

    All cones are cubes.

    All cubes are decagons.

    No diagonal is a cube.

    Conclusions:

    I. Some diagonals are polygons.

    II. All diagonals are decagons.

    III. No polygon is a cone.

    IV. Some cubes are angles.

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