Analyzing the Letter Series Pattern

The given series of letters is C, B, B, C, Z, E, W, H, S, ?, N. To solve this type of letter series question, we usually look for patterns based on the alphabetical positions of the letters or observe repeating sequences or progressive changes.

Let's write down the alphabetical position for each letter:

Looking at the series, it doesn't follow a simple single pattern. Let's try splitting the series into two interwoven series, one consisting of the letters at odd positions (1st, 3rd, 5th, etc.) and the other at even positions (2nd, 4th, 6th, etc.).

Identifying the Interwoven Series

Series 1 (Odd Positions): C, B, Z, W, S, N

Let's look at the positions of these letters:

• C (3rd)
• B (2nd)
• Z (26th)
• W (23rd)
• S (19th)
• N (14th)

Now, let's find the difference in their positions:

• B to C: $2 - 3 = -1$
• Z to B: $26 - 2 = -2$ (considering wrapping around from B backwards to Z)
• W to Z: $23 - 26 = -3$
• S to W: $19 - 23 = -4$
• N to S: $14 - 19 = -5$

The pattern in Series 1 is a decreasing difference in alphabetical position: $-1, -2, -3, -4, -5$.

Series 2 (Even Positions): B, C, E, H, ?

Let's look at the positions of these letters:

• B (2nd)
• C (3rd)
• E (5th)
• H (8th)
• ? (10th position in the original series)

Now, let's find the difference in their positions:

• C to B: $3 - 2 = +1$
• E to C: $5 - 3 = +2$
• H to E: $8 - 5 = +3$
• ? to H: This difference should follow the pattern.

The pattern in Series 2 is an increasing difference in alphabetical position: $+1, +2, +3, \dots$ The next difference should be $+4$.

Finding the Missing Letter

The missing letter is at the 10th position in the original series, which is the 5th term in Series 2. The pattern for Series 2 differences is $+1, +2, +3, +4, \dots$. The last known letter in Series 2 is H (8th position). The difference between the letter before H (which is E) and H was $+3$. The next difference should be $+4$.

So, the position of the missing letter will be the position of H plus 4.

Position of H is 8.

Position of missing letter = Position of H $+ 4 = 8 + 4 = 12$.

The letter at the 12th position in the English alphabet is L.

Therefore, the letter that replaces the question mark is L.

Revision Table: Letter Series Analysis

Additional Information on Letter Series Reasoning

Letter series questions are common in logical reasoning tests. They assess your ability to identify patterns and relationships between letters in a sequence. Common patterns include:

• Adding or subtracting a constant number to the alphabetical position (e.g., A, C, E, G... where the difference is +2).
• Adding or subtracting an increasing or decreasing number (e.g., A, B, D, G, K... where differences are +1, +2, +3, +4...). This is similar to the pattern found in Series 2 of our problem.
• Alternating patterns or multiple interwoven series, as seen in the problem above.
• Skipping letters in a specific pattern.
• Reversing the alphabetical order.
• Using vowel or consonant sequences.

To solve these problems effectively, it's helpful to know the alphabetical position of each letter quickly. Writing down the series and trying different pattern approaches (like splitting into sub-series) is a good strategy.