Numerical series tests are a type of numerical aptitude test which require you to find the missing number in a sequence. This missing number may be at the beginning or middle but is usually at the end. In Numerical ability test, numbers are used in a particu­lar pattern in order to form a series. Your task, here is to find out the pattern with which the numbers form a se­ries and on that basis to fill up the missing numbers. There are various patterns to form a number series. Let us examine some common series.
Simple series

1. Addition or Subtraction
a) Even numbers
Eg.(l) 2,6,12,20,30,42,-,-Answer is 56,72 - can be obtained by adding even num­bers 4,6,8,10,12,14,16
b) Odd numbers.
Eg.(l) 60,59,56,51,44, -, -Answer is 35,24 - can be obtained bysubtracting odd numbers 1,3,5,7,9,11,….
c) Prime numbers
(Prime Number is a positive number ( >0 ) that is divisible only by 1 and itself. )Eg.(l) 2,3,5,8,13,20,-,-Answer: 31,44 - can be obtained by adding prime num­bers 1, 2, 3, 5, 7, 11, 13 etc.

2. Divide the number to get the next one.
Eg: 64, 32, 16,8, -,- Answer: 4, 2 is obtained by going on dividing by 2.

3. Ascending /Descending order:
The series may be in ascending or in descending orderEg: 10,8,6.4,-
Answer: 2
Take the square root of the number to get the next one.
Eg: 65536, 256,16, -,-
Answer: 4, 2.

4. Take the square root of the number to get the next one.
Eg: 65536, 256,16, -,-
Answer: 4, 2.

More Complex structures
Sometimes many series are operated together; insuch a case examine each one separately.
Eg: 5, 8, 6, 10.7. 12, 8,-,-
Answer: 14, 9- Two series are here; one series is 5,6,7,8,(next number -9) and the other is 8,10,12,(next number -14)

Here you can see another complex series.
3, 6, 11, 18, -
The interval, beginning with 3, increases by 2 each time so the next will be 27.

Another example:
How many six are there in the following series which are immediately either precede by 4 or followed by 7 ?
3129647646729764467
Choices: 1,2,3,4
This is really twisting .But so simple if analysed closely. First pick only six and check whether it precede by 4 or followed by 7. Yes the answer is 2.

Q.Find out the missing number 15 16 18, 21,25, 30, 50,58, -

1.     60
2.     63
3.     67
4.     69

Q.What should be the missing fraction in the given series? 4/9,9/20,----,39/86

1.     17/40
2.     20/45
3.     19/42
4.     39/44

Q.Find out the missing number 5,14,15,24,25,34,35,-

1.     44
2.     45
3.     55
4.     54

Q.Find out the missing number: 1 5 25 125, 3 12 - 192, 7 14 28 56

1.     40
2.     58
3.     48
4.     64

Q.Fill in the blanks in this series: 47, 32, -, 11, 5, 2

1.     20
2.     10
3.     15
4.     25

Q.Supply the missing figure: 3, 11, 8, 16, 13, 21,-

1.     18
2.     21
3.     24
4.     27

Q.11, 12, 17, 18, 23, 24, -

1.     35
2.     29
3.     32
4.     36

Q.What number comes next? 196, 16, 144, 36, 100, -

1.     65
2.     46
3.     64
4.     84

Q.5, 7, 13, 23, 29, 55, -, -

1.     60, 96
2.     61, 119
3.     59, 89
4.     69, 86

Q.1, 3, 2, -, 3, 7

1.     6
2.     5
3.     9
4.     7