9th Class Mental Ability Series Completion Series Completion

Series Completion

Category : 9th Class


A series made up of alphabetical letters or numerals or combination of both may have one or more terms missing, one term wrong etc.

You have to find out the missing term(s) or identify the wrong term in the question from the given options.


Trick: To solve such problems first identify the rule on which the given series has been generated.



To Find out Missing Term(s)

In these type of questions, a series is given in which one or more terms are missing usually marked with '?'.

You have to find out the right option by identifying the rule to continue the series.






1.  Find out the missing term marked with '?'.   

                                    \[-\,4,7,29,\text{ }62,?\]

     (a) 95                                   (b) 106                          (c) 62                            (d) 102


Explanation (b):

We observe that,

The pattern is +11, +22, +33, + 44

So, 5th term = 44 + 4th term = 44 + 62 =

That is,



2.  Find out the missing terms each marked with (?) in the series given below.

B, C, ?, H, L, ?, W

     (a) E, Q                    (b) D, N                         (c) E, M                         (d) D, Q


Explanation (a):



3.  Find out the missing term to replace the mark '?'.

hlp, txb, fjn, rvz, ?

     (a) aei                      (b) cgk                           (c) dhl                           (d) dfh


Explanation (c):

In each term, there is a gap of 3 letters between any two consecutive letters.

Also there is a gap of 3 letters between the last letter of a term and the first letter of the next term.


4.  Find out the missing letters in alphabetical series given below.

b_a b_a_ca_c_be_

     (a) abcabc                (b) abbcca                     (c) ccbbaa                                  (d) aabbcc


Explanation (c):

The complete given series is bca/bca/bca/bca/bca. Clearly, the pattern bca is repeated.


5.  Find out the missing term.

     H4J, ?, F9N, E13P, D18R

    (a) I5K                       (b) G6L                         (c) MOL                        (d) T7Z


Explanation (b):

1st characters:

Middle characters:

3rd characters:




To Find Out Wrong Term

In this type of questions, a series is given of which one term does not follow the rule on which the series has been generated. You have to find out such term from the alternatives followed by the question.



6.  Find the wrong term in the given series.

     2, 4, 16, 32, 128,250, 1024

     (a) 16                       (b) 128                          (c) 250                          (d) 1024


Explanation (c):

The correct pattern is \[\times 2,\text{ }\times 4,\text{ }\times 2,\text{ }\times 4,....\]

So, 250 is wrong that must be replaced by \[128\times 2=256.\]



7.  Choose the wrong term in the following number series.

169, 144, 120, 100, 81

     (a) 81                       (b) 100                          (c) 120                          (d) 144


Explanation (c):

The sequence is 132, 122, 112, 102/ 92 i.e., 169, 144, 121, 100, 81

So, 120 is wrong term.



8.  Choose the wrong term in the given series.


    (a) BCY                     (b) CDX                         (c) EFV                          (d) EFW


Explanation (d):

1st letters: A, B, C, D, E

2nd letters: B, C, D, E, F

3rd letters: Z, Y, X, W, V

Clearly, the wrong term is EFW.

It must be replaced by DEW.

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