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Series Completion

Series completion is an integral part of the Reasoning Ability Test and finds place in the various competitive exams,entrance exams etc. The series may be of numbers or alphabets.

The following type of questions are asked in a series completion test;

Find the missing number:


3, 7, 15, 31, 63, 127, _
The sequence being followed in this question is
1st number x 2+1 = 2nd number.
2nd number x 2+1 = 3rd number.
Hence the series will be completed by 127 x 2 + 1 = 255

Replace the wrong term:


6, 10, 27, 105, 515, 3084
The sequence being followed in this series is as under;
6 x 2 - 2 = 10
10 x 3 - 3 = 27
27 x 4 - 4 = 104
104 x 5 - 5 = 515
515 x 6 - 6 = 3084
The fourth term 105 is wrong.

Find the missing alphabet:


C F L _ O R
The series follows 3rd, 6th, 9th, 12th, 15th and 18th letter of alphabet. This missing alphabet, therefore is L.

Instead of one alphabet series, there can be a series of groups of alphabets in which the candidate has to find the missing group.

Find the wrong group of Alphabets: In these type of questions a series of groups of alphabets is given in which one group is wrong. The candidate has to replace it with the correct group find it and if asked.

The letters and numbers can be mixed to make a series like A2B, C3D, E4F or MN 20, OP 25, QR 30, ST 35 etc.

Capital letters and small letters can also be mixed to make a series MnI KJi, HGf, DCb or TuV, NoP, HiJ, BcD.