In the following alphabet pattern question, four two letter groups are given (AJ, EN, NW and PW). In three of these groups, the second letter is 9 positions ahead of the first letter in the alphabet, while one group has a different gap. Select the odd letter group from the given alternatives.

Introduction / Context:
This question checks your ability to recognise fixed gaps between letters in the English alphabet. You are given four letter pairs: AJ, EN, NW and PW. In most of these pairs, the second letter is a fixed number of positions ahead of the first letter. One pair does not follow the same alphabetical gap. Your goal is to find the pair that breaks the pattern and mark it as the odd one out.

Given Data / Assumptions:

• Letter pairs: AJ, EN, NW and PW.
• Alphabet positions: A = 1, B = 2, ..., Z = 26.
• We compare the positions of the first and second letters in each pair.
• Three pairs share the same positive gap, while one pair has a different gap.
• No other hidden coding rule is assumed.

Concept / Approach:
The approach is very direct: convert letters to their numerical positions and subtract the first position from the second. If three pairs have a difference of +9 and one pair has a different difference, that pair is the odd one. Fixed gap patterns like +3, +5 or +9 are common in letter series questions, so training yourself to quickly compute these differences can speed up your performance in reasoning sections.

Step-by-Step Solution:
Step 1: Analyse AJ.A = 1 and J = 10. Difference: 10 - 1 = 9. So AJ has a gap of +9.Step 2: Analyse EN.E = 5 and N = 14. Difference: 14 - 5 = 9. EN also has a gap of +9.Step 3: Analyse NW.N = 14 and W = 23. Difference: 23 - 14 = 9. NW again has a gap of +9.Step 4: Analyse PW.P = 16 and W = 23. Difference: 23 - 16 = 7. The gap here is +7, not +9.Step 5: Identify the odd pair.Since AJ, EN and NW all use a +9 jump, PW with a +7 jump is the odd letter group.

Verification / Alternative check:
You can also perform a quick mental check by counting forward from each first letter. From A, count nine letters forward (including the next letter), you land at J. From E, nine letters ahead is N. From N, nine letters ahead is W. But from P, nine letters ahead would be Y, not W. This again confirms that PW has a different spacing and therefore does not fit the rule followed by the other three pairs.

Why Other Options Are Wrong:
AJ: Second letter is 9 positions ahead of the first, fitting the main pattern.
EN: Also shows a gap of +9 and is therefore not odd.
NW: Has the same +9 gap and belongs with AJ and EN.

Common Pitfalls:
Some candidates might attempt to see meaning based connections between letters or read them as abbreviations. In examination settings, patterns are usually purely positional. Another common error is miscounting the number of steps between letters, especially under time pressure. Writing down the numerical positions or counting carefully on fingers or a rough diagram helps avoid small arithmetic mistakes.

Final Answer:
The odd letter group is PW, because its letters differ by 7 positions in the alphabet, whereas the other three pairs all have a fixed gap of 9 positions between the first and second letters.