2021 CSAT, all questions
UPSC Prelims 2021 · CSAT
Question 48: Logical Reasoning and Mental Ability
Which day is 10^th October, 2027 ?
aSunday
bMonday
cTuesday
dSaturday
AnswerUPSC’s answer is (a).
Count odd days from a known date. 10 October 2021 was a Sunday. From 10 October 2021 to 10 October 2027 is six years, with one leap day (29 February 2024). That is 6 × 365 + 1 = 2191 days, and 2191 = 7 × 313, so the day of the week is unchanged. 10 October 2027 is a Sunday. Remember: a normal year shifts the weekday by one and a leap year by two, so these six years shift it by 5 + 2 = 7, which is zero.
Why each option is right or wrong
- (a) Right: 2191 days is exactly 313 weeks, so the day stays Sunday.
- (b) Monday would need a shift of one day; the total shift is 0.
- (c) Tuesday would need a shift of two days; the total shift is 0.
- (d) Saturday would need a shift of six days; the total shift is 0.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2021, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.