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Question

In the following series, one term is missing as shown by the question mark(?). Select the missing term from the given options.
A, BC, DEF, GHIJ, ?

This question was previously asked in
RRB ALP 2018 CBT 2 Fitter Question Paper (21-Jan-2019) (Shift 3)
The correct answer is

KLMNO

Understanding Letter Series Patterns

This question asks us to identify the missing term in a given letter series: A, BC, DEF, GHIJ, ?. Letter series questions test our ability to recognize patterns in sequences of letters based on their position in the alphabet.

Analyzing the Given Letter Series

Let's look at the terms provided in the series:

  • Term 1: A
  • Term 2: BC
  • Term 3: DEF
  • Term 4: GHIJ
  • Term 5: ?

Identifying the Pattern in the Series

We need to find a consistent rule that connects each term to the next. Let's examine two aspects: the number of letters in each term and the starting letter of each term.

Number of Letters Pattern

Let's count the number of letters in each known term:

  • Term 1 (A) has 1 letter.
  • Term 2 (BC) has 2 letters.
  • Term 3 (DEF) has 3 letters.
  • Term 4 (GHIJ) has 4 letters.

The number of letters in each subsequent term increases by 1. Following this pattern, the missing Term 5 should have 4 + 1 = 5 letters.

Starting Letter Pattern

Now let's look at the starting letter of each term and compare it to the last letter of the previous term:

  • Term 1 starts with A.
  • Term 2 starts with B. The last letter of Term 1 is A. B is the letter immediately after A.
  • Term 3 starts with D. The last letter of Term 2 is C. D is the letter immediately after C.
  • Term 4 starts with G. The last letter of Term 3 is F. G is the letter immediately after F.

The pattern for the starting letter is that each term begins with the letter immediately following the last letter of the preceding term.

Determining the Missing Term

Based on the identified patterns, we can find the missing Term 5:

  1. Number of Letters: Term 4 has 4 letters. Term 5 should have 4 + 1 = 5 letters.
  2. Starting Letter: The last letter of Term 4 (GHIJ) is J. Term 5 should start with the letter immediately after J, which is K.

So, the missing term is a sequence of 5 letters starting with K. These letters are K, L, M, N, O.

Therefore, the missing term is KLMNO.

Comparing with Options

Let's compare our derived term, KLMNO, with the given options:

  • Option 1: XYZA (4 letters) - Incorrect.
  • Option 2: PQRS (4 letters) - Incorrect.
  • Option 3: KLMNO (5 letters, starts with K) - Correct.
  • Option 4: TUVW (4 letters) - Incorrect.

The missing term that fits the pattern is KLMNO.

Term Letters Number of Letters Starting Letter Last Letter Relation to Previous Term
1 A 1 A A -
2 BC 2 B C Starts after previous term's end (A → B)
3 DEF 3 D F Starts after previous term's end (C → D)
4 GHIJ 4 G J Starts after previous term's end (F → G)
5 ? 5 K O Starts after previous term's end (J → K)

Conclusion

The pattern involves increasing the number of letters by one in each subsequent term and starting each term with the letter immediately following the last letter of the previous term. Following this pattern, the term after GHIJ is KLMNO.

Revision Table: Letter Series Pattern

Aspect Pattern Observed Application for Missing Term
Number of letters Increases by 1 in each term (1, 2, 3, 4, ...) The missing term should have 4 + 1 = 5 letters.
Starting letter The letter immediately after the last letter of the previous term. The previous term ends in J. The next term starts with K.

Additional Information: Types of Letter Series

Letter series questions can have various types of patterns. Some common patterns include:

  • Alphabetical Position: Patterns based on the position of letters in the alphabet (A=1, B=2, etc.).
  • Skip Letters: Skipping a fixed number of letters between terms or within terms.
  • Reverse Alphabetical Order: Letters moving backwards in the alphabet.
  • Combination of Patterns: Combining different rules, such as number of letters and letter position.
  • Alternating Patterns: Two different patterns running alternately in the series.

Solving letter series requires careful observation and logical deduction to identify the underlying rule.

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Important Questions from Alphabet Series

  1. A series is given with some letters missing. Choose the correct alternative from the given ones that will complete the series:

    BR __ __ NB __ O __ NB
  2. A series is given with some letters missing. Choose the set of letters which when sequentially placed shall complete it .

    a __ __ dba __ __ bcad __ __ da __ __ cd
  3. In the following letter series, some of the letters are missing which are given in that order as one of the alternatives below It. Choose the correct alternative

    _ a _ b _ abaa _ bab _ abb
  4. Select the combination of letters that when sequentially placed in the blanks of the given series will complete the series.

    Q _ P _ M _ A _ T _ Q A _ T M

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