Solving the Letter Series Pattern

The question asks us to identify the letters that will complete the given series: WA _ D _ B C _ W _ C D W D C _. To solve this type of problem, we need to look for a repeating pattern or sequence within the letters when the blanks are filled.

Analyzing the Given Series and Options

The series has 15 letters and 5 blanks, for a total of 20 positions. We are given four options, each containing 5 letters to fill these blanks. Let's examine the series with the first option, CWDCD, filling the blanks from left to right:

Original series with blanks:

WA _ D _ B C _ W _ C D W D C _

Filling the blanks with CWDCD:

WA C D W B C D W C C D W D C D

The completed series becomes: WACDWBCDWCCDW DCD

Identifying the Pattern in the Completed Series

Let's look at the completed series WACDWBCDWCCDWDCD and try to find a repeating pattern. We can try grouping the letters. Let's try grouping into sets of 4 letters:

WACD | WBCD | WCCD | WDCD

Looking at these four groups, we can observe a clear pattern:

• Each group starts with the letter W.
• Each group ends with the letters CD.
• The second letter in each group follows an alphabetical sequence: A, B, C, D.

So, the pattern is a sequence of four blocks: WACD, followed by WBCD, followed by WCCD, followed by WDCD.

Mapping the Pattern to the Blanks

Now let's compare this identified pattern (WACD WBCD WCCD WDCD) to the original series with blanks (WA _ D _ B C _ W _ C D W D C _) to see if the letters we used from option 1 correctly fill the blanks according to this pattern.

Let's write the original series positions and the pattern positions:

Note: The original series had 15 fixed letters and 5 blanks, totaling 20 positions when filled.

From the table and the pattern WACD WBCD WCCD WDCD, the letters filling the blank positions are:

• Blank 1 (Position 3) = C
• Blank 2 (Position 5) = W
• Blank 3 (Position 8) = D
• Blank 4 (Position 10) = C
• Blank 5 (Position 15) = D

The sequence of letters filling the blanks is CWDCD. This exactly matches Option 1.

Therefore, placing the letters CWDCD in the blanks from left to right completes the letter series according to the identified pattern.

Revision Table: Letter Series Concepts

Additional Information: Types of Letter Series Patterns

Letter series questions in reasoning tests can follow various patterns. Recognizing these can help solve problems faster. Some common types include:

• Alphabetical Order: Letters follow sequential order (A, B, C...) or reverse order (Z, Y, X...).
• Skipping Letters: Letters skip a fixed number of letters (A, C, E - skips 1 letter).
• Combination of Letters: Groups of letters repeat or change in a specific way (like AB, BC, CD...).
• Position in Alphabet: The pattern might relate to the numerical position of letters (A=1, B=2...).
• Repeating Blocks: A fixed block of letters repeats (ABC, ABC, ABC...).
• Changing Blocks: Blocks repeat but with internal changes, as seen in this problem (WACD, WBCD...).
• Mixed Patterns: Patterns combining letters and numbers or other symbols.

To excel at letter series problems, practice identifying different types of patterns and systematically test possibilities.