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07. Verbal Reasoning for TCS Placement Papers -- LETTER SERIES - Concept & Types of Letter Series

                                                     In these types of problems a series of the letters of alphabet will be given which follow a pattern or a sequence.
To solve this type of problems assign number 1 to 26 to the letters of the alphabet as shown below. In some cases it is useful to assign the number in the reverse order.
1   2    3  4   5   6  7   8   9  10 11 12  13  14 15 16  17 18  19  20  21 22 23  24 25 26
  B   C  D  E   F  G   H   I    J  K   L    M   N   O   P   Q   R   S    T    U  V  W   X   Y   Z
26 25  24 23 22 21 20 19 18 17 16 15 14 13 12 11   10  9   8    7    6   5   4    3  2   1
The letter series mainly consists of skipping of the letters.
Some of the patterns of alphabet series may be as follows:
1)   Equal numbers of letters are missed. Ex in ‘ADE’ etc. two following letters are missed.
2)   One following and the other preceding the letter may be organized, Ex: in YZX letter Y is following and X is proceeding.
3)   When numbers are mixed with letters, the numbers may refer to the position of the letters in the alphabets.
Ex: D4, H8, L12…
4)   Pattern may be according to the position of letters in alphabets, Example in EJO the first letter is fifth, the second is tenth and the third is ninth in the alphabets.
5)   Remember that after ‘Z’ there will come ‘A’ in the sequence because the counting is circular.   
One Letter Series:
Example 1: B, E, H, K, N, ___
a) Q                  b)P               c)O               d)S               e)F
Answer: Clearly the given series is (+3)
B+3=E,         E+3=H,         H+3=K,         K+3=N
 The next letter is N+3=Q.

Example 2: O, P, R, U, Y, ____
a)    C                  b) D              c) E              d) F              e)H
Answer: Here, the series is +1, +2, +3, +4, etc
O+1=P, P+2=R, R+3=U, U+4=Y
Hence , the answer is  Y + 5 =D

Example 3: X, V, T, R, P, ___
a)    A                  b) P                       c) N                       d) B
Answer: Clearly, Each term moved 2 steps back word obtains the next term.
So the answer P-2= N

Example  4 : Z, X, V, T, R, (…….. ), (……… )
a) 0, K   b) N, M  c) K, S  d) P, N
Ans. Clearly, the given series consists of alternate letters in a reverse order. So, the missing terms would be P and N. Hence, the answer is d.

Example 5 : J, Z , I ,Y , H ,_
a)    A                 b)X               c) z              d)G
Explanation: The letters in the given series go backward alternatively. So previous letter to Y is X.

Two Letter Series:
The first letters of the series follow one logic and the second letters follow logic. Also the first two letters, the next two letters and so on follow logic.

Example 6: LA, NC, PE, RG, ___
a)       TI       b) SI   c) VH  d) TH
Answer:  The First letters of the terms is L, N, P, R  +2 series.
               The second letters of the terms are A, C, E, G (+2) Series.
The next term is R+2, G+2  = TI

Example 7 : nd, iy , dt, yo, tj ?
(a)     mp (b) nq (c) of (d) oe                           
Ans. Clearly, the first and second letters of each term are moved five steps backward to obtain the corresponding letters of the next term.
Hence, the answer is (d).

Three Letter Series:
This sequence consists of 3 letters in each term. The first letters follow one logic, the second letters follow some other logic and the third letters follow some other logic, (or the same logic in all the three cases).
Example 8 . ABC, CBA, DEF, FED, GHI,..........                                          
a) JKL b) IHG           c) DFE d)IJK                                                     
 Ans : 2. The second term is the reverse order of first    term.                                                                               In addition to the above types a number of other types can also be identified.

Example 9: BDF, CFI, DHL,…..?
 (a) CJM    (b) ElM   (c) EJO   (d) EMI                                    
Ans. Clearly, the first, second and third letters of each term are respectively moved one, two and three steps forward to obtain the corresponding letters of the next term. So, the missing term is EJO. Hence, the answer is (c).

Miscellaneous Series:

Example 10 : - P 3 C, R 5 F, T 8 I, V 12 L, ?
(a)Y170   (b) X17M   (c) X170   (d) X160
Ans :-Clearly, the first letters of the terms are alternate. The sequence followed by the numbers is + 2, + 3, + 4, … . The last letter of each term is three steps ahead of the last letter of the preceding term. Thus, the next term would be X 17 O. Hence, the answer is (c)

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