SBI PO- Number Series- Tips & Mistakes to Avoid

The State Bank of India Probationary Officer exam Prelims phase is going to be conducted on the 2nd, 4th, and 5th August 2025. As very few days are left for the prelims exam, and quants is one of the scoring sections. Talking about the quants section, number series is one such topic where, if you keep certain things in mind and avoid mistakes, then you will be able to achieve a good score. In this blog, we are going to discuss the same. 

What is a Number Series?

A series of numbers that are sequenced in a pattern, or following a particular rule. You have to either find out the missing number or identify the wrong number in the given set. This is to check the candidate’s ability to solve problems with quick accuracy, and also tests pattern recognition that will ultimately help the candidates to find loopholes in the system. 

Common Patterns in SBI PO Number Series

Certain common patterns are usually asked in SBI PO Number series. They are given in the table below.

Pattern Type	Example
Addition/Subtraction	2, 4, 8, 16, 32,? → 64
Multiplication/Division	2, 4, 8, 16, 32, ? → 64
Prime Numbers	1, 8, 27, 64,? → 125
Squares/Cubes	1, 8, 27, 64, ? → 125
Alternate Patterns	1, 2, 6, 24, 120,? → 720
Mixed Operations	1, 1, 2, 3, 5, 8,? → 13
Fibonacci Series	5, 9, 17, 33,? → 65
Difference of Differences	5, 9, 17, 33, ? → 65

Tips to Solve Number Series Quickly

To stay ahead in the competition, one needs to master speed along with accuracy. To solve number series quickly, here are a few tips given below.

Observe the Gap Between Numbers

Start by observing the pattern between the consecutive numbers. Check whether the pattern is based on addition, subtraction, or a difference of squares/cubes.

Check for Multiplication/Division

If the difference between the numbers is increasing or decreasing rapidly, then check for multiplication and division logic. Example- Series: 3, 6, 18, 72, 360,?

Step 1: Observe differences

• 6 – 3 = 3
  
• 18 – 6 = 12
  
• 72 – 18 = 54
  
• 360 – 72 = 288
  
• → The gap increases rapidly. Try multiplication.
  

Step 2: Try multiplying consecutive terms

• 3 × 2 = 6
  
• 6 × 3 = 18
  
• 18 × 4 = 72
  
• 72 × 5 = 360
  
• 360 × 6 = 2160

Answer- 2160

Look for Common Series Types

Look out for patterns, such as is the series contains squares, cubes, etc. Example-

Question: 1, 8, 27, 64, ?, 216
What comes in the blank?

Solution:
This is a cube series:
1³, 2³, 3³, 4³, _ , 6³
→ 5³ = 125

Answer: 125

Spot Alternating Patterns

Sometimes, two different types are merged into one. So check the pattern carefully. Example- Example:

Series: 2, 5, 4, 9, 8, 17, ?

Firstly, Split into two series based on alternate positions:

• Odd-position terms: 2, 4, 8,?
  
• Even-position terms: 5, 9, 17
  

Analyze Odd-position Series:

2 → 4 → 8 → ?

• 2 × 2 = 4
  
• 4 × 2 = 8
  
• 8 × 2 = 16
  

Next odd-position term = 16

Analyze Even-position Series:

5 → 9 → 17 → ?

• 5 + 4 = 9
  
• 9 + 8 = 17
  
• 17 + 16 = 33
  

 Next even-position term = 33

Combined Series:

2 (1st)
5 (2nd)
4 (3rd)
9 (4th)
8 (5th)
17 (6th)
16 (7th)
33 (8th) → would be the next after 16

Final answer- 16

Use Approximation

If the calculation is more complex and time-consuming, try to solve the question approximately. As it will save your time and many times, options are also given in approximation.

Practice Shortcut Tricks

Practice shortcut tricks such as n²±n, n×n±1, Doubling and adding/subtracting a fixed number

Examples of the above short tricks are-

Trick: n²±n

Example:

Series: 2, 6, 12, 20, 30,?

Let’s test the pattern:

• 1² + 1 = 1 + 1 = 2
  
• 2² + 2 = 4 + 2 = 6
  
• 3² + 3 = 9 + 3 = 12
  
• 4² + 4 = 16 + 4 = 20
  
• 5² + 5 = 25 + 5 = 30
  
• 6² + 6 = 36 + 6 = 42
  

Answer: 42

Trick: n×n±1

Example:

Series: 0, 3, 8, 15, 24,?

Let’s analyze the pattern:

• 1×1 – 1 = 1 – 1 = 0
  
• 2×2 – 1 = 4 – 1 = 3
  
• 3×3 – 1 = 9 – 1 = 8
  
• 4×4 – 1 = 16 – 1 = 15
  
• 5×5 – 1 = 25 – 1 = 24
  
• 6×6 – 1 = 36 – 1 = 35
  

Answer: 35

Doubling and Adding/Subtracting a Fixed Number

Example:

Series: 3, 7, 15, 31, 63,?

Let’s find the logic:

• 3 × 2 + 1 = 6 + 1 = 7
  
• 7 × 2 + 1 = 14 + 1 = 15
  
• 15 × 2 + 1 = 30 + 1 = 31
  
• 31 × 2 + 1 = 62 + 1 = 63
  
• 63 × 2 + 1 = 126 + 1 = 127
  

Answer: 127

Common Mistakes to Avoid in Number Series

Here are a few mistakes that are quite repeated by the candidates while solving number series, but if you can avoid these mistakes, it will result in better scores. 

Assuming the Pattern Too Early

Without fully understanding the pattern, if you assume the answers quickly, then it can be a blunder, especially in mixed pattern cases. 

Ignoring Alternate Patterns

Carefully examine the pattern in alternate number sets. Often, candidates do not analyze it and just tick the options, which results in the wrong answer.

Panicking Under Time Pressure

Many times, when the students don’t get the pattern in the number series, they start panicking, but instead of that, one should keep calm and try to focus on analyzing or recognizing the patterns, and this can be achieved only by practicing daily.  

Conclusion

In this blog, we have given all the tips and tricks to solve number series in SBI PO Exam along with the mistakes that one should avoid to get better scores. As very few days are left, and if you want to brush up your skills and check the level of your preparation, then you can join our mock test series. The link is given below. 

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