SSC CGL Reasoning · Series
Wrong Term Series
One term in the series breaks the rule: find the rule from the terms that agree, predict each term in turn, and the first term that does not match is the wrong one.
Why this matters
Twenty-three questions in the bank, 21 from the 2025 shifts and two from the 2024 shifts: twelve MODERATE and eleven EASY. Nineteen hide one or two wrong numbers in a number series and four hide a wrong cluster or letter-and-number term. Every rule from the earlier pages can appear here, so this page comes last.
Concept 1 of 2: Find the rule from the terms that agree
Definition
1. Find the rule from the start of the series, using the earlier pages: differences, ratios, squares and cubes, or two series woven together. 2. Predict each term in turn from the one before. Stop at the first term that does not match. 3. Replace it with the predicted value and check that the next printed term follows from the corrected one. If it does, you have the wrong term. 4. Two wrong terms: these questions usually weave two series together, one wrong term in each. Check the odd and even places separately. 5. Fast route: a wrong term is often just one or two away from the right value, and the options list only four candidates, so test the options rather than the whole row.
Worked example
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
Example 1 · Series · Wrong Term Series
Blaming the term after the break
Changing the rule to fit the wrong term
Concept 2 of 2: The wrong cluster or term
Definition
- Inside each cluster: look at the steps between its letters (BDF is +2, +2). The right clusters usually share them.
- From cluster to cluster: follow the first letters (B, E, H, K) as a letter series.
- Letter-and-number terms: check the letter series and the number series separately; the wrong term breaks one of them.
- The correct version of the wrong cluster is a good last check: it should fit both rules.
Worked example
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
Example 2 · Series · Wrong Term Series
Checking only one direction
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)
- Blaming the term after the break→ Find the rule from the terms that agree
- Changing the rule to fit the wrong term→ Find the rule from the terms that agree
- Checking only one direction→ The wrong cluster or term
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.