Cheat Sheet: Number Series
Number Series questions test your ability to identify patterns among numbers using basic arithmetic, logic, and observation.
You are given a sequence with one term missing, and you must find that missing number.
This topic is highly scoring because:
- Concepts are limited
- Patterns repeat across exams
- Speed improves sharply with practice
Weightage of Number Series in Bank Exams
Exam | No. of Questions | Marks |
|---|---|---|
IBPS PO Prelims | 4-5 | 4-5 |
IBPS Clerk Prelims | 4-5 | 4-5 |
SBI PO Prelims | 5 | 5 |
SBI Clerk Prelims | 4-5 | 4-5 |
RBI Assistant | 5 | 5 |
Average Weightage: 15-20% of Reasoning / Quant section
1. Arithmetic Series
Based on addition or subtraction of a fixed number.
Example: 2, 5, 8, 11, ?
Pattern: +3
Answer: 14
2. Geometric Series
Based on multiplication or division.
Example: 3, 6, 12, 24, ?
Pattern: ×2
Answer: 48
3. Squares and Cubes
Squares: \(1^2, 2^2, 3^2, 4^2\)
Cubes: \(1^3, 2^3, 3^3, 4^3\)
Example: 1, 4, 9, 16, ?
Answer: 25
4. Alternating Series
Two different patterns alternate.
Example: 2, 6, 4, 12, 8, ?
Odd terms: 2, 4, 8 (×2)
Even terms: 6, 12 (×2)
Answer: 24
5. Difference Series
Difference between consecutive terms forms a pattern.
Example: 5, 11, 19, 29, ?
Differences: 6, 8, 10
Next difference = 12
Answer: 41
6. Second Difference Series
Used when first differences are irregular.
Example: 2, 7, 16, 29, ?
First difference: 5, 9, 13
Second difference: 4, 4
Answer: 46
7. Prime Number Series
Sequence of prime numbers.
Example: 2, 3, 5, 7, 11, ?
Answer: 13
8. Mixed Logic Series
Combination of operations.
Example: 3, 10, 31, 94, ?
Pattern: ×3 + 1
Answer: 283
9. Fraction Series
Numerator and denominator follow patterns.
Example: 1/2, 2/3, 3/4, 4/5, ?
Answer: 5/6
10. Common Formulas
Sum of first n natural numbers: \( S = \frac{n(n+1)}{2} \)
Sum of squares: \( S = \frac{n(n+1)(2n+1)}{6} \)
Sum of cubes: \( S = \left(\frac{n(n+1)}{2}\right)^2 \)
FAQs on Cheat Sheet: Number Series
| 1. What is the significance of number series in bank exams? |  |
| 2. How are number series questions generally structured in bank exams? | |
| 3. What types of patterns are commonly found in number series questions? | |
| 4. What strategies can candidates use to solve number series questions effectively? | |
| 5. How much weightage do number series questions carry in bank exams? | |
