<h2>Two stage types series</h2>

 In a two steps series the difference

 of the concecutive numbers

 them selves form an arithmetic 

or geometric series

 

 Example 1      3, 5,  9, 15, 23, ?

 Calculate the differences of the terms

 5-3=2 

 9-5=4 

 15-9=6 

23-15=8 

The series of the differences is: 2, 4, 6, 8, ... 

This is an arithmetic progression d=2 

the next number in AP is 8+2=10

 So the next term in the example series is 23+10=33

 

Example 2

 Find the missing number in the following set:

3, 10, 24, x, 108, 220

 Calculate the differences between 

those that are next to each other.

10-3=7

24-10=14

108-52=56

220-108=112

 

The number series of the differences is:

7,14, x, 56, 112

Notice that every term is multiple by 2

7X2=14        56X2=114

The number series is GP with common ratio 2

So the number series of differences is:

7, 14, 28, 56,  112

 

Therefore the missing number is:

24+28=52

 Τhis Type Number series is very common in competitive exams

 The Two Stage Type Series is a series in which

 the difference between consecutive terms forms a series of its own.

 

 

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 Number series basic concept
Number series types for competitive exams
Detailed examples for each type of number series