Solving the Letter Series Completion Problem

This question asks us to find the letter cluster that completes a given series: ABDG, BCEH, ?, DEGJ, EFHK. To solve this type of series completion problem, we need to identify the pattern or rule that governs the progression from one letter cluster to the next.

Analyzing the Pattern in the Letter Series

Let's look at how the letters change between consecutive known terms in the series:

1. From ABDG to BCEH
2. From DEGJ to EFHK

We can examine the change in each letter's position in the English alphabet (A=1, B=2, C=3, ...):

It appears that each letter in the cluster is shifting forward by one position in the alphabet to get the corresponding letter in the next cluster. Let's confirm this pattern with the next pair:

The pattern is consistent: each letter in a cluster is advanced by one position in the alphabet to obtain the next cluster in the series.

Applying the Pattern to Find the Missing Cluster

The missing cluster is between BCEH and DEGJ. We need to apply the same +1 shift rule to the letter cluster BCEH to find the missing term.

• First letter: B → C (B + 1 position)
• Second letter: C → D (C + 1 position)
• Third letter: E → F (E + 1 position)
• Fourth letter: H → I (H + 1 position)

Following this pattern, the missing letter cluster is CDFI.

Verifying the Missing Term

Now, let's check if applying the +1 shift rule to CDFI results in the next known term, DEGJ.

• First letter: C → D (C + 1 position)
• Second letter: D → E (D + 1 position)
• Third letter: F → G (F + 1 position)
• Fourth letter: I → J (I + 1 position)

Yes, applying the pattern to CDFI yields DEGJ, which matches the given series. Therefore, the missing letter cluster is indeed CDFI.

Conclusion

The letter cluster that replaces the question mark (?) to complete the given series ABDG, BCEH, ?, DEGJ, EFHK is CDFI.

Revision Table: Letter Series Pattern

Additional Information on Series Completion Reasoning

Series completion questions in reasoning tests can involve various patterns, not just simple shifts. Some common types include:

• Arithmetic Progression: A constant number is added or subtracted from the terms (for number series).
• Geometric Progression: Terms are multiplied or divided by a constant factor (for number series).
• Alphabetical Shifts: Letters shift by a fixed number of positions (like in this question), or the shift amount changes.
• Alternating Patterns: Different rules apply to alternate terms.
• Combination Patterns: A mix of rules (e.g., shift increases by one each time, or numbers and letters are combined).
• Positional Patterns: The pattern relates to the position of the letters or numbers.

To solve these questions, it's crucial to carefully observe the differences or relationships between consecutive terms and hypothesize a rule. Testing the hypothesized rule against subsequent terms helps confirm the pattern and find the missing element.