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Q39·CSAT · Prelims 2022

Syllogism evaluation with 'some' and 'all' propositions

ReasoningSyllogismFactual single● Medium

Question

Three Statements followed by three Conclusions are given below. You have to take the Statements to be true even if they seem to be at variance from the commonly known facts. Read all the Conclusions and then decide which of the given Conclusions logically follows/follow from the Statements, disregarding the commonly known facts: Statement-1: Some doctors are teachers. Statement-2: All teachers are engineers. Statement-3: All engineers are scientists. Conclusion-I: Some scientists are doctors. Conclusion-II: All engineers are doctors. Conclusion-III: Some engineers are doctors.

Options

a

Only Conclusion-I

b

Only Conclusion-II

c

Both Conclusion-I and Conclusion-III

Answer
d

Both Conclusion-I and Conclusion-II

Explanation

Construct the logical chain from the premises:

1D \cap T \ne \emptyset (There is an overlap between Doctors and Teachers).
2T \subset E (All Teachers sit inside the Engineers circle).
3E \subset S (All Engineers sit inside the Scientists circle).

Because the Teacher overlap zone (D \cap T) is fully swallowed by the Engineer circle (E), and then entirely swallowed again by the Scientist circle (S), that specific group of Doctor-Teachers automatically becomes Doctor-Engineers and Doctor-Scientists.

Evaluate Conclusions:

I: Some scientists are doctors. (True. The overlap zone guarantees this).
II: All engineers are doctors. (False. Only the specific overlap section is guaranteed).
III: Some engineers are doctors. (True. The overlap zone guarantees this).

Conclusions I and III logically follow.

When an overlapping set ("Some A are B") is caught in a chain of supersets ("All B are C, All C are D"), the initial overlapping subjects carry through the entire chain (Some A are C, Some A are D).

Answer: (c).

Question details

Year

2022

Paper

CSAT

Question

Q39

Section

Logical & Analytical Reasoning

Sub-topic

Syllogism

Type

Factual single

Difficulty

Medium

Source hint

Some doctors are teachers. All teachers are engineers.

Same sub-topic — other years

Syllogism has appeared in multiple CSAT papers:

Q47

2024

Deducing logical conclusions from standard categorical syllogisms

ReasoningEasy

Q48

2024

Deducing logical conclusions from categorical syllogisms with negative premises

ReasoningMedium

Q78

2023

Deductive logic from conditional statements

ReasoningMedium

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