In the expression 5 * 4 * 3 * 2 * 1, * is chosen from +, -, × each at most two times. What is the smallest non-negative value of the expression?
- (a) 3
- (b) 2
- (c) 1
- (d) 0 ✓ UPSC's answer
Why the answer is (d)
• There are four operator slots in 5 * 4 * 3 * 2 * 1, and each of +, −, × may be used at most twice.
• Try 5 − 4 − 3 + 2 × 1: − is used twice, + once and × once, which is allowed.
• By BODMAS, 2 × 1 = 2, so the value is 5 − 4 − 3 + 2 = 0.
• A value below 0 would be negative, so 0 is the smallest non-negative value — option (d).
Why the other options are wrong
- (a) 3
- The value 3 is not the smallest possible non-negative value since 0 is achievable.
- (b) 2
- The value 2 is not the smallest possible non-negative value since 0 is achievable.
- (c) 1
- The value 1 is not the smallest possible non-negative value since 0 is achievable.
Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2024, held on 16 June 2024. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.