Number Series is a very interesting topic. While it comes under the reasoning section for SSC and various other exams, for banking and insurance aspirants, number series is a part of quantitative aptitude. Although the types of questions asked in both exams differ, the process of solving and identifying patterns remains similar.
In this blog, we have provided all the details about the types of questions in Number Series, along with key concepts, strategies, tips, and tricks to solve them.
What Is Number Series in Quantitative Aptitude and Reasoning?
Number Series is a logical sequence of numbers arranged according to a specific rule or pattern. Aspirants have to identify the rule and find the missing number or identify the incorrect term.
This topic tests:
- Logical reasoning
- Pattern recognition
- Mathematical operations
- Speed and accuracy
It frequently appears in exams to assess your analytical thinking and numerical agility.
Why Is Number Series Important in Competitive Exams?
Number series is an important topic, and questions from this section appear in every exam. The number of questions asked in these exams is as follows:
| Exam | No. of Questions | Difficulty |
| SSC CGL / CHSL | 1–2 | Easy |
| IBPS PO / SBI PO | 1–2 | Moderate |
| RRB NTPC / Group D | 1 | Easy |
| State PSC / Police | 1–2 | Moderate |
Types of Number Series Questions
Number series questions are of various types. The details of the different types of number series questions are as follows:
| Types | Details |
| Arithmetic Series | Increases/decreases by a constant difference |
| Geometric Series | Multiplied/divided by a constant ratio |
| Square/Cube Series | Based on perfect squares or cubes |
| Alternating Series | Pattern alternates in a regular cycle |
| Mixed Series | Combination of operations or multi-step patterns |
| Wrong Number Series | One number doesn’t follow the rule |
| Missing Number Series | One blank or “?” to be identified |
Concepts of Number Series Questions
Different types of concepts for solving number series questions are as follows:
| Concept | Explanation |
| Arithmetic Pattern | Constant addition/subtraction |
| Geometric Pattern | Constant multiplication/division |
| Alternating Series | Every second/third term follows a different rule |
| Square/Cube Series | Based on n², n³, etc. |
| Prime Numbers Series | Sequence involving prime numbers |
| Difference Pattern | Use of 1st, 2nd or 3rd level differences |
What Are the Different Forms of Number Series Questions?
The different forms of number series questions are as follows:
- Direct Number Series – Find the next/missing number in a straightforward sequence
- Wrong Number Series – Identify the incorrect number that breaks the pattern
- Puzzle-based Series – Requires decoding a hidden or complex logic
- Coded Number Series – Numbers may represent values based on coding
- Mixed Concept Series – Involves combination of arithmetic, geometric, and logical patterns
Formulas to Solve Number Series Questions
Different formulas (or logical patterns) to solve number series questions are as follows:
- Check first-level and second-level differences
- Identify multiplication or division patterns
- Look for alternate term logic
- Use reverse logic when terms decrease
- Break complex series into two parallel series
Number Series Tricks for SSC CGL and Other Exams
Tricks to solve number series questions are as follows:
- Start by finding the difference between terms
- Check for multiplication/division patterns
- Use the square/cube of position numbers (1², 2²…)
- Check alternate terms separately
- Don’t stick to one logic – think flexibly
- Use options to eliminate quickly
- Memorize common series like primes, squares, cubes
- Reverse-check the pattern if unsure
Solved Number Series Questions from 2024–25 Exams
Question 1:
Exam: SSC CGL 2024 Tier 1 Shift 2 – Memory-Based
Q: 2, 4, 8, 16, 32, ?
Ans: 64
Explanation: Multiplying by 2 every step → 32 × 2 = 64
Question 2:
Exam: IBPS PO Prelims 2024 – Memory Based
Q: 121, 144, 169, 196, 225, ?
Ans: 256
Explanation: These are consecutive perfect squares: 11², 12², … → 16² = 256
Question 3:
Exam: RRB NTPC 2024 CBT-1 – Memory-Based
Q: 3, 6, 11, 18, 27, ?
Ans: 38
Explanation: Differences: +3, +5, +7, +9, +11 → next = 27 + 11 = 38
Question 4:
Exam: SBI PO Mains 2024 – Memory Based
Q: 2, 6, 18, 54, ?, 486
Ans: 162
Explanation: Multiply by 3 each time → 54 × 3 = 162
Number Series Concepts for Bank Exams
In banking exams like IBPS PO or SBI PO, number series often involve:
- Coded patterns (e.g., reverse square roots)
- Multi-step logic (difference + ratio)
- Reverse or backward series
Example:
Q: 200, 100, 50, 25, ?
A: 12.5 (Divide by 2 at each step)
These require fast decoding and mental agility.
Common Mistakes to Avoid while Solving Number Series
While solving Number Series Quantitative Aptitude questions candidates must keep the below mentioned details in mind:
- Assuming only one type of pattern (e.g., only addition)
- Ignoring alternate term logic
- Skipping second-level difference check
- Spending too much time on a single question
- Not practicing mixed or coded patterns
What Are Related Topics I Should Revise Next?
Topics you should revise next are as follows:
- Questions based on Time and Distance
- Rules and Practice Questions of Simplification
- Shortcuts and Patterns of Ratio and Proportion
- Various types of Questions Based on Data Interpretation
- Tricks & Examples of Inequalities
FAQs
Start by checking the first-level difference between terms. If no fixed pattern appears, check for:
Second-level differences
Multiplication/division patterns
Square/cube or alternating logic
Calculate the expected pattern between terms. The number that doesn’t fit the logic is the incorrect one.
Start checking from both ends and focus on the middle terms where patterns usually change.
In alternating series, every second or third number follows a different rule.
Example: 2, 4, 3, 6, 4, 8…
→ First, third, fifth: +1
→ Second, fourth, sixth: ×2
Yes. Some key tricks include:
Use the difference method first
Look for multiplication/square-based jumps
Spot alternate logic
Back-calculate if needed
Eliminate options using logic
Spend no more than 30–40 seconds on a Number Series question. If unsure, mark for review and come back later to avoid time loss.
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Hi, I’m Tripti, a senior content writer at Oliveboard, where I manage blog content along with community engagement across platforms like Telegram and WhatsApp. With 3+ years of experience in content and SEO optimization related to banking exams, I have led content for popular exams like SSC, banking, railways, and state exams.