SSC CGL Reasoning · Series
Alphanumeric and Pattern Series
Terms that mix letters with numbers are two or three small series in one: solve the letters and the number separately. A few series instead shuffle the letters of a word or follow a known order.
Why this matters
Twenty-three questions in the bank, two from the 2023 shifts, thirteen from the 2024 shifts and eight from the 2025 shifts: 21 EASY and two MODERATE. Fifteen are letter-and-number terms like FM61 where each part moves on its own, three weave two series together or pair a letter with its own position, and five rearrange letters or follow an order such as the levels of life. Each uses only the letter and number rules from earlier pages.
Concept 1 of 3: Letters and numbers as separate series
Definition
- Split each term into its letter columns and its number.
- Solve each part with the earlier pages: positions and steps for the letters, differences or ratios for the number.
- Fast route: the number part is usually quickest. Work it out first and strike out every option with the wrong number; then check the letters of what is left.
- The number can come first (3P, 6N, 12L): the method is the same.
Worked example
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
Example 1 · Series · Alphanumeric and Pattern Series
Right letters, wrong number
Concept 2 of 3: Two series woven together, and letters with their positions
Definition
- Check odd and even places separately when next-door terms look unrelated.
- A letter with its own position: C3, X24. The number is the letter's place from A, so it confirms the letter.
- A letter with its reverse position: A26, C24. The number is 27 minus the letter's place.
- Decide which series the answer belongs to by counting its place.
Worked example
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
Example 2 · Series · Alphanumeric and Pattern Series
Continuing the wrong series
Concept 3 of 3: Rearranged letters and word series
Definition
1. Number the letters of the first term 1, 2, 3, and so on. 2. Write where each letter of the next term came from, for example 3, 1, 2, 5, 4. 3. Test the same order on the next pair. If it does not work, find the second order: SSC series often switch between two orders. 4. Apply the right order to the last term. 5. Word series: the terms follow an order you know, such as days, months, the Greek letters (Alpha, Beta, Gamma, Delta, Epsilon) or the levels of life (atom, molecule, cell, tissue, organ). 6. Digit patterns such as 111X222, 222X333 move each part on by one.
Worked example
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
Example 3 · Series · Alphanumeric and Pattern Series
Using one order for every step
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Watch out for (3)
- Right letters, wrong number→ Letters and numbers as separate series
- Continuing the wrong series→ Two series woven together, and letters with their positions
- Using one order for every step→ Rearranged letters and word series
Test yourself on Series
20 past SSC CGL questions from this chapter, timed at 12 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.