How to solve Alphanumeric Series Questions?

I will discuss the concepts related to alphanumeric series in reasoning tests. I will also guide you through various example questions and their solutions in this category.

What is Alphanumeric Series?

Alphanumeric Series is a series/sequence/combination of alphabets, symbols, and numbers. Alphabets can be lowercase(a-z) or uppercase(A-Z). Symbols can be like @#$%^&*().

Sometimes these series can also contain punctuation marks like “,;.” as well.

Let’s check an example.

N B # 6 H 8 I O 0 P @ ! 4 * D Q 4 5 A

So now you know what is Alphanumeric series. Now definitely you’ll be interested to know what to what kind of questions can be asked in competitive exams in this category.

Find Next in Alphanumeric Sequence

The first category of questions in alphanumeric series is where you’ll be given a sequence. The sequence will follow a special logic to determine the next item in the sequence. You’ll be asked to find the next item in the sequence. Check this example.

Question What should be the next in this sequence?
L49, N64, P81, R100, T121, ??.

This question is fairly simple. You just need to crack the logic of getting the next number in the sequence.

Steps to be followed

1. We clearly see that for each item in the sequence we have alphabet and number. So if there is any logic, then the next item will also have an alphabet and a number.

2. So first let’s find the alphabet.
Currently, alphabets are in sequence L, N, P, R, T. Observe closely, these are alphabets in sequence by skipping 1 place. L..M..N..O..P..Q..R..S..T.
Clearly next alphabet should be V (after skipping U).

3. Let’s find the number.
Currently, we see number sequence as 49, 64, 81, 100, 121
If you practice reasoning questions good enough, you should see that these are squares of smaller numbers in sequence.

(7)2 , (8)2 , (9)2 , (10)2 , (11)2 ..

TIP: You should remember about the squares and cubes of at least the first 20 numbers, to save time.

Clearly next in the sequence is (12)2 = 144

4. So, from 1, 2, and 3, we can clearly see that the answer should be T144.

I took a simple example to explain to you the concept and approach.

Questions around Type of Characters in Alphanumeric series

In this category, you’ll be given 1 alphanumeric sequence of letters/characters.

You’ll be asked about the questions based on the type of symbols or the symbols which are following or proceeding with another type of symbol.

Again repeating – Type of symbols include alphabets, numbers, special symbols, punctuation marks, etc.

Let’s check another example.

Question You are given a sequence

M 4 E 6 S F I P V B 2 N 3 L 0 A I C B
How many numbers in the above sequence, each of which is immediately followed by a consonant and preceded by a vowel?

To solve the above problem, you need to know about vowels and consonants in the English alphabet.

Tip: There are 5 Vowels in English i.e. A, E, I, O, U.

Tip: Consonants include all other alphabet characters except vowels.


Step 1 Count the numbers in the sequence which are followed by a consonant. ( followed by means coming before. e.g. A is followed by B in alphabet.)

Alphanumeric sequence - example - step 1
Alphanumeric sequence – example – step 1

Clearly, 6 is followed by consonant S, 2 is followed by consonant N, 3 is followed by consonant L.

Step 2: Out of the above cases, find how many of them are preceded by a Vowel ( A E I O U). (Preceded by means, coming after)

Alphanumeric sequence - example - step 2
Alphanumeric sequence – example – step 2

6 is preceded by E which is a vowel,

2 is preceded by B, non-vowel.

3 is preceded by N, non-vowel.

So there is only 1 number, i.e 6 in the given alphanumeric series which is immediately followed by a consonant and preceded by a vowel.

So the answer to the above question is 1.

The key to solving this question is, how quickly you can do step 2 and step 1.

Also, can you do both steps in 1 go?

Let’s take another example.

Question: M 4 E 6 S F I P V B 2 N 3 L 0 A I C B

If we remove all vowels from this alphanumeric series, What would be the 5th element from the right?

So what we need to do is remove all vowels from the series and count the 5th element from the reverse side.

Alphanumeric sequence example solution 2
The solution of Example 2

Step 1 Remove all vowels.
Step 2 Count symbols from the right.

from the figure above, it is clear that the answer is 3.

Questions based on operations on Alphanumeric series

In this category also, one alphanumeric sequence will be given to you. You may be asked to perform certain operations on each symbol/item in the sequence.

When you perform operations on that sequence, you get a new sequence. Then you are asked questions on the new sequence.

Let me demonstrate with another example.

Question You are given a sequence

How many vowels would be there in the sequence, if each letter in the sequence is increased by 3 (i.e. A + 3 = D, J + 3 = M)?

Steps to solve

Step 1: Before we count a number of vowels, we need to increase each letter in the sequence by 3.

Step 2: Count the number of vowels. Check the figure below.

Alphanumeric Series questions sample - 3

Clearly answer is 3.

The main challenge in these questions is how quickly you can apply the operation and tell the answer.


There might be some questions that can be a combination of the above types of questions. The key is practice and clear concepts.

If you have any doubts, please write us in the comments section.

Leave a Comment