In the following question, four three-letter groups are given: FHJ, LNQ, JLN and NPR. In three of these groups, the letters progress through the alphabet with equal jumps of two positions each, while one group does not follow this pattern. Which letter group is the odd one out?

Introduction / Context:
This question belongs to the letter series and odd one out category in aptitude tests. You are given four groups of letters and asked to identify which group does not follow the same alphabetical pattern as the others. These questions test your skills in mapping letters to their positions in the English alphabet and recognising consistent step sizes between them.

Given Data / Assumptions:

• Letter groups: FHJ, LNQ, JLN, NPR.
• We use the standard positions: A = 1, B = 2, ..., Z = 26.
• We will examine the step difference between consecutive letters in each group.
• We assume that exactly one group will break the established pattern.

Concept / Approach:
In many letter pattern questions, the difference in alphabetical positions between letters is constant. For example, a sequence might move +2 positions each time. Here, we will calculate the position difference between the first and second letters, and between the second and third letters, for each group. If three groups share the same pattern (for example, +2 and +2) and one group does not, that group is the odd one out.

Step-by-Step Solution:
Step 1: For FHJ: F = 6, H = 8, J = 10. Differences: H - F = 8 - 6 = 2, J - H = 10 - 8 = 2. So the pattern here is +2, +2. Step 2: For JLN: J = 10, L = 12, N = 14. Differences: L - J = 12 - 10 = 2, N - L = 14 - 12 = 2. This also follows a +2, +2 pattern. Step 3: For NPR: N = 14, P = 16, R = 18. Differences: P - N = 16 - 14 = 2, R - P = 18 - 16 = 2. Again, the pattern is +2, +2. Step 4: For LNQ: L = 12, N = 14, Q = 17. Differences: N - L = 14 - 12 = 2, Q - N = 17 - 14 = 3. Step 5: Here, LNQ has step sizes +2 and +3, while all the other groups strictly have +2 and +2. Step 6: Therefore, LNQ is the only letter group that does not follow the same equal-jump pattern and is the odd one out.

Verification / Alternative check:
To verify quickly, you can mentally check if each sequence looks like equally spaced letters. FHJ, JLN and NPR all look like evenly spaced letters in the alphabet. In contrast, LNQ appears slightly stretched, especially in the jump from N to Q. This quick alphabet check confirms our detailed numeric analysis.

Why Other Options Are Wrong:
FHJ is not odd because both jumps, F to H and H to J, are exactly 2 letters apart. JLN is not odd because both jumps, J to L and L to N, are also 2 letters apart. NPR is not odd because N to P and P to R both involve a jump of 2 letters. Only LNQ, with jumps of +2 then +3, breaks the equal step pattern.

Common Pitfalls:
A common mistake is to miscount the number of steps between letters, especially when doing it quickly in your head. Another pitfall is focusing only on whether the letters are generally moving forward without checking if the distances are consistent. Always convert letters to numbers and compute exact differences to avoid such errors in letter reasoning questions.

Final Answer:
The letter group that does not maintain equal jumps of two positions and is therefore the odd one out is LNQ.