🗺️ Chapter Roadmap
1 The Logic of a Series
In almost every IQ and competitive test (NTS, CSS, GAT), you will find Number Series questions. You are given a sequence of numbers that follow a Hidden Rule. Your goal is to identify that rule and predict the next number in the line.
The Golden Strategy:
Always check the Difference between the first two or three numbers first. If the difference is constant or follows its own pattern, you've solved 90% of series problems!
2 Addition (+) & Subtraction (−)
If the numbers in the series are increasing or decreasing slowly, the hidden rule is usually based on addition or subtraction.
Constant Change
2, 5, 8, 11, ?
Rule: Adding 3 every time.
Next: 11 + 3 = 14
Increasing Change
2, 4, 7, 11, 16, ?
Rule: +2, then +3, then +4, then +5...
Next: 16 + 6 = 22
3 Multiplication (×) & Division (÷)
If the numbers are exploding (increasing very fast) or shrinking quickly, the rule is almost always multiplication or division.
🚀 Exponential Growth Pattern
2 × 2 = 4
4 × 2 = 8
8 × 2 = 16...
Next Number: 32 × 2 = 64
4 Exam Traps (Squares & Primes)
Sometimes the numbers don't seem to have a difference or multiplication rule. This is when you check for Special Sequences:
Square Series
Logic: These are perfect squares of numbers (1², 2², 3², 4², 5²).
Next: 6² = 36
Prime Series
Logic: Numbers that cannot be divided by anything except 1 and themselves.
Next: 17 (Not 15!)
5 Complex Series Logic
🌊 Fibonacci Sequence
In this sequence, you get the next number by adding the previous two numbers together.
(Logic: 5 + 8 = 13)
🔄 Alternating Series
There are actually two separate series jumping over each other! Look for a pattern in the 1st, 3rd, and 5th numbers.
(Logic: 10, 20, 30... so next is 40)