UPSC Prelims 2026 · CSAT
Question 29: Basic Numeracy
Three variables x, y and z take values 2, 3, 4 or 5 such that their values are always distinct. If M and N denote the largest possible value and the smallest possible value, respectively, for the expression {(x × y) + z}; then M − N is
AnswerUPSC’s answer is (c).
For (x × y) + z with distinct values from 2, 3, 4, 5: the largest product is 5 × 4 = 20, and z = 3 (not 2) gives 23, so M = 23. For the smallest, take the smallest product 2 × 3 = 6 with z = 4, giving 10; any other choice is larger (for example 2 × 4 + 3 = 11), so N = 10. Then M − N = 13.
Why each option is right or wrong
- (a) Wrong: 11 does not equal 23 − 10.
- (b) Wrong: 12 does not equal 23 − 10.
- (c) Right: 23 − 10 = 13.
- (d) Wrong: 14 does not equal 23 − 10.
Only the provisional key (27 May 2026) was found; the final key replaces it when found.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2026, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.