D-D-R-S-C: Difference → Double Difference → Ratio → Squares → Cubes. Try in this order and you'll crack 90% of series.
Number Series Tricks
SBI POIBPS POSSC CGLRRB
Items to Memorize
- Difference Method (constant/increasing differences)
- Double Difference Method
- Ratio Method (multiply pattern)
- Square Series (n², n²±k)
- Cube Series (n³, n³±k)
- Fibonacci-type (sum of previous two)
- Alternate Series (two patterns interleaved)
- Prime Number Series
- Geometric Progression (×2, ×3, ×1.5)
- Mixed Operation Series (+2, ×3, +4, ×5...)
Mnemonic Tricks
How It Maps
| Cue | Maps To |
|---|---|
| D (Difference) | Check if differences between terms are constant or form a pattern |
| D (Double Diff) | If differences aren't constant, take difference of differences |
| R (Ratio) | Divide each term by the previous — look for constant multiplier |
| S (Squares) | Check if terms are near perfect squares (n², n²+1, n²-1) |
| C (Cubes) | Check if terms are near perfect cubes (n³, n³±n) |
Why It's Faster
Banking exams use these 5 patterns in 90% of series questions. Working through them in order ensures you never waste time on the wrong approach.
For wrong-number-in-series: find the pattern for ALL terms, then check which single term breaks it. The odd one out is your answer.
Why It's Faster
SBI PO specifically uses 'which number is wrong' format rather than 'find the next number'. Knowing this saves you from solving the wrong way.
Frequently Asked Questions
How to solve number series quickly in banking exams?
Follow the D-D-R-S-C order: check Differences first, then Double differences, Ratios, Squares, and Cubes. This systematic approach covers 90% of banking exam series patterns.
What is the most common number series pattern in SBI PO?
Mixed operation series (alternating addition and multiplication) and wrong-number-in-series format are the most frequently asked. Practice identifying the pattern break.
How many number series questions come in SBI PO Prelims?
Typically 5 questions in Prelims, almost always in the wrong-number format. These are free marks if you practice the pattern recognition method.