In the letter series L J H J P D P ? E, which letter should replace the question mark so that the series follows a consistent pattern?

Introduction / Context:
This problem is a letter series question where you must identify the pattern connecting successive groups of letters. Such series often hide numeric relationships based on alphabetical positions rather than obvious repetition. The goal is to find a consistent rule that applies throughout the sequence and then use that rule to determine the missing term. Developing a habit of translating letters to numbers and looking for patterns greatly helps with this type of reasoning item.

Given Data / Assumptions:
The given series is L, J, H, J, P, D, P, ?, E. We are asked to find which letter should replace the question mark. The options given are K, L, P, I and M. We assume that there is a single consistent pattern governing all the letters and that only one option fits this pattern correctly. The pattern may involve groupings within the series rather than simple left to right differences.

Concept / Approach:
A powerful approach is to group the series into equal sized blocks and then look for numeric relationships within each block. Here, grouping the nine letters into three blocks of three gives us L J H, J P D and P ? E. After converting each letter to its position in the alphabet and examining the sums or differences inside each block, a clear pattern can emerge. If we find that two blocks obey a particular rule, we can impose the same rule on the third block to solve for the unknown letter.

Step-by-Step Solution:
Write the series as three groups of three: (L, J, H), (J, P, D) and (P, ?, E). Convert each letter to its alphabetical position: L = 12, J = 10, H = 8, P = 16, D = 4 and E = 5. Compute the sum of the positions in each known group: L + J + H = 12 + 10 + 8 = 30, and J + P + D = 10 + 16 + 4 = 30. This shows that each complete group of three letters has a total value of 30 in terms of alphabetical positions. For the third group P, ?, E we must therefore have 16 + (position of ?) + 5 = 30. So the missing position is 30 - 21 = 9, which corresponds to the letter I, since I is the ninth letter of the alphabet.

Verification / Alternative check:
To verify, check that with I as the missing letter, all three groups follow the same total sum rule. The third group P I E gives 16 + 9 + 5 = 30, matching the totals of the first two groups. Now test each of the other option letters in place of the question mark and recompute the sum. Using K (11), L (12), P (16) or M (13) would give sums of 32, 33, 37 or 34 respectively, which break the pattern. Therefore, only I preserves a consistent group total of 30. This confirms that the reasoning is correct and I is uniquely determined.

Why Other Options Are Wrong:
If K were used, the third group would sum to 32, not matching the required 30. With L the sum becomes 33, while P leads to 37 and M gives 34, all inconsistent with the first two groups. There is no alternate simple pattern that fits all nine letters while using any of these alternatives. Since the series is expected to have one clean numeric rule, any option breaking the total sum of 30 for each group must be rejected. This leaves I as the only viable choice.

Common Pitfalls:
One common mistake is to look only at consecutive differences between neighbouring letters, which appear irregular and confusing in this series. Another pitfall is to assume repetition based patterns without testing them numerically, leading to random guesses. Students sometimes forget to consider grouping as a strategy, even when the total number of terms divides neatly into equal blocks. To avoid these issues, always try converting letters into numbers and experiment with sums or symmetric patterns. When multiple groups show identical sums, products or differences, that is often the key to unlocking the missing term.

Final Answer:
The letter that fits the pattern in the series L J H J P D P ? E is I.