How to solve questions on Alphanumeric Series?

Alphanumeric (sometimes shortened to alphameric) is a combination of alphabetic and numeric characters. In some cases, it may include upper and lower case letters, punctuation marks, and symbols (such as @, &, and *,). Questions based of alphanumeric series are commonly asked in various competitive exams.
This type of reasoning is a mixed bag of coding-decoding, series-based reasoning and finding positions based reasoning questions.
Points to note:
Before jumping to the questions, let us understand the meaning of few key words that are generally used in such questions like "following, followed by, preceding, and preceded by".
  • Let us take two successive alphabets Y and Z. Here, Y is preceding Z and Z is preceded by Y. Also, Z is following Y and Y is followed by Z.
  • Now, take three successive alphabets: X, Y and Z. Here X and Y are preceding Z, but Y is immediately preceding Z whereas, X is not immediately preceding Z. Similarly, Y and Z are following X, but Y is immediately following X whereas, Z is not immediately following X.
Alphanumeric Series: Solved Examples
DIRECTIONS (Example no. 1-5): Study the following digit-letter-symbol sequence carefully and answer the questions given below:
4 P + S r 9 B # A 3 ? 7 c > Z % 6 d & Q @ 1
Example 1: If the above sequence is written in the reverse order, then which element will be 5th to the right of 16th element from the right end?
Solution: Reversed Sequence - 1 @ Q & d 6 % Z > c 7 ? 3 A # B 9 r S + P 4.
Hence, now the 16th element from the right end is % and 5th to the right of % is ?
Shortcut method: There is an alternate way to find the answer without writing the sequence in reverse order. Since both the directions are given from right, subtract them: 16R - 5R = 11R
Now, as the questions asks the sequence to be reversed, the element is 11th from left of the original series, i.e. '?'.
Example 2: How many such numbers are there in the above sequence, each of which is immediately preceded by a consonant and immediately followed by a symbol?
Solution: Check for the sequence Consonant-number-symbol. There is only 1 such case in the above sequence: A 3 ?
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Example 3: Which element is seventh to the left of sixteenth element from the left in the above sequence?
Solution: The sixteenth element from the left is %. Now, we move 7th to the left of %, which is A. Hence, A is be the answer.
Shortcut method: Since both the directions are given from left, we will subtract them: 16L - 7L = 9L
So, the 9th element from left is A.
Example 4: If the first half of the series is written in reverse order, then which element will be fourteenth from the right end?
Solution: There are a total of 22 characters in the above sequence. Since, the first half of the above sequence is reversed, therefore, the sequence is:
? 3 A # B 9 r S + P 4 7 c > Z % 6 d & Q @ 1So, the required 14th character from right is '+'.
Shortcut method: There is another way to solve the question without reversing the first half of the series. Since there are a total of 22 characters in the sequence, the first half contains 22/2 = 11 characters.
Subtracting, we get: 14R - 11R = 3R. For the reversed half, it will be 3rd element from the left of the original series, i.e. '+'.
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Example 5: Which element will be fourteenth from the right end, if second half of the series is reversed?
Solution: There are total 22 characters given in the above sequence. As only the second half is reversed the sequence becomes:
4 P + S r 9 B # A 3 ? 1 @ Q & d 6 % Z > c 7. So, the required 14th character from right is A.
Note: If you see carefully, you can find the answer without reversing the second half. As each half contains 22/2 = 11 characters, the 14th character from right end will be in the first half. 
So, it can be directly found from the original series; 14th character from right of the original series is 'A'. 
Alphanumeric Series: Key Learning
  • One of the most scoring question-type in any competitive exam is alphanumeric series puzzles. These questions are high scoring as they can be solved very quickly.
  • Learning shortcuts to handle these types of questions will significantly boost your reasoning score. Hence, try to practice as many questions as you can.
For any query on any concept or example, feel free to post in the comment section below.