UPSC Prelims 2016 · CSAT

Question 10: Logical Reasoning and Mental Ability

Consider the following statement : “We shall go either for a picnic or for trekking”. Which of the following, if true, would falsify this claim ?

aWe go for a picnic but not for trekking

bActivities such as picnic and trekking are encouraged by the health authorities

cWe go for trekking and not for picnic

dWe do not go either for picnic or for trekking

AnswerUPSC’s answer is (d).

'Either A or B' promises that at least one of the two will happen. The only way to make that promise false is for neither to happen, which is option (d). If we do at least one of them, the promise holds as normally read. A remark about health authorities has no bearing on what we actually do. Remember: to falsify an either-or statement, show the case where both alternatives fail.

Why each option is right or wrong

(a) A picnic without trekking keeps the claim true.
(b) Says nothing about what we actually do.
(c) Trekking without a picnic keeps the claim true.
(d) Right: neither activity happening is the case that breaks the claim.

Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2016, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.