2014 CSAT, all questions
UPSC Prelims 2014 · CSAT
Question 76: Logical Reasoning and Mental Ability
If the 3rd day of a month is Monday, which one of the following will be the fifth day from 21st of this month ?
aMonday
bTuesday
cWednesday
dFriday
AnswerUPSC’s answer is (c).
Count days by remainders on division by 7. The 3rd is Monday, so the 21st is 18 days later; 18 leaves remainder 4, so the 21st is a Friday. Five days after the 21st is the 26th, five days after Friday: Wednesday. Check: the 26th is 23 days after the 3rd, 23 leaves remainder 2, and Monday plus 2 days is Wednesday.
Why each option is right or wrong
- (a) Monday would need a gap of 21 or 28 days from the 3rd; the gap to the 26th is 23.
- (b) Tuesday would need a gap with remainder 1; the gap of 23 days has remainder 2.
- (c) Right. 23 days after a Monday is a Wednesday.
- (d) Friday is the weekday of the 21st itself, not the 26th.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2014, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.