Number, Letter and Alphanumeric Series
Find the rule that makes every term: test differences, then changing differences, ratios, alternation and special series. Letters become numbers (A = 1 … Z = 26), and mixed terms are split into parts.
What it is
A series (or sequence) is a list of numbers, letters or letter-number groups that follows a rule. You are asked for the next term (or a missing one). Your job is to find the one rule that produces every given term, then use it once more.
A series item usually shows 5 to 7 terms. A good item has exactly one rule that fits all the terms shown.
Why it matters on the exam
Series items appear in both the Professional and Sub-Professional tests, and the practice tests give whole sets of number, letter and alphanumeric series. They are fast points once you have a fixed checklist; without one, you can waste minutes guessing.
The same habit of looking for a rule helps in data work, for example spotting the pattern in file codes or reference numbers.
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The rest of this lesson, and every other lesson, is part of ReviewTayo.
Read moreIn the full lesson
- How to recognize it on the test
- What to look for (6 checks)
- All 8 rules and tools
- 4 worked examples, every step explained
- 6 common mistakes and how to fix them
- 3 exam techniques
- Remember: 6 key points
- Practice questions with explanations, and your progress saved
More Numerical Ability lessons
ReviewTayo has 47 lessons that follow the official scope of the exam, each with rules, worked examples, common mistakes and practice. Open one and read the first part.