Three of the following are alike in some way and one is different. Select the odd one.

The working rule here is the digit sum. Add the digits of each option: A) 5878 gives 5+8+7+8 = 28. B) 5788 gives 5+7+8+8 = 28. C) 9748 gives 9+7+4+8 = 28. D) 6482 gives 6+4+8+2 = 20. Three options total 28 and one totals 20, so D is the odd one out.

The core concept is simple digit arithmetic. Many aspirants look for a pattern in the order of the digits, such as ascending order, primes, or mirror symmetry, and spend time on it. Checking the digit sum first is faster. A and B are also rearrangements of the same digits (5, 7, 8, 8), which confirms the sum is the intended link.

Trap: Aspirants often spot that A and B share digits and conclude that A, B and C are alike because of that. C does not share digits with A or B, so the common property must be the sum. Test one property across all four options before accepting a pattern.

This is a Prelims reasoning and aptitude skill rather than a Mains topic. Quick pattern checks like this reduce time pressure in the CSAT-style reasoning section.