UPSC Prelims 2020 CSAT Paper II · Q32 of 80 Logical Reasoning easy

Two Statements are given followed by two Conclusions : Statements : All numbers are divisible by 2. All numbers are divisible by 3. Conclusion-I : All numbers are divisible by 6. Conclusion-II : All numbers are divisible by 4. Which of the above Conclusions logically follows/follow from the two given Statements?

  1. (a) Only Conclusion-I ✓ UPSC's answer
  2. (b) Only Conclusion-II
  3. (c) Neither Conclusion-I nor Conclusion-II
  4. (d) Both Conclusion-I and Conclusion-II

Why the answer is (a)

• The first statement establishes that every number in the set is divisible by 2.

• The second statement establishes that every number in the set is also divisible by 3.

• Since 2 and 3 are co-prime integers, any number divisible by both must be divisible by their least common multiple, which is 6.

• Therefore, Conclusion-I logically follows from the combination of the two statements.

• Conclusion-II claims divisibility by 4, but being divisible by 2 does not guarantee divisibility by 4 (e.g., 2 is divisible by 2 but not 4).

• Thus, only Conclusion-I is valid, making option (a) the correct answer.

Why the other options are wrong

(b) Only Conclusion-II
Conclusion-II does not follow because divisibility by 2 does not imply divisibility by 4.
(c) Neither Conclusion-I nor Conclusion-II
Conclusion-I does logically follow because any number divisible by both 2 and 3 is divisible by 6.
(d) Both Conclusion-I and Conclusion-II
Conclusion-II does not follow, so it is incorrect to say both conclusions follow.

Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2020, held on 4 October 2020. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.

Reading the answer is not the same as getting it right under a clock. Practise this question with UPSC's negative marking, and anything you miss goes into an error notebook until you get it right twice.

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