2022 CSAT, all questions
UPSC Prelims 2022 · CSAT
Question 75: Logical Reasoning and Mental Ability
What is the value of X in the sequence 2, 12, 36, 80, 150, X?
a248
b252
c258
d262
AnswerUPSC’s answer is (b).
Each term fits n³ + n²: 1 + 1 = 2, 8 + 4 = 12, 27 + 9 = 36, 64 + 16 = 80, 125 + 25 = 150. The sixth term is 216 + 36 = 252. A check by differences: 10, 24, 44, 70 have second differences 14, 20, 26 and a constant third difference of 6, which points to a cubic; the next difference is 102, and 150 + 102 = 252.
Why each option is right or wrong
- (a) 248 does not fit n³ + n².
- (b) Correct: 6³ + 6² = 252.
- (c) 258 does not fit n³ + n².
- (d) 262 does not fit n³ + n².
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2022, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.