# Number Series – Find Missing Number (01)

Number Sequence is one the important part of logical reasoning syllabus and its questions are repeatedly asked in competition exams like GMAT, CAT, CMAT and other government entrance exams like SSC, SBI-PO, IBPS, NDA, AFCAT, NABARD, PSC examinations.

Here are the lists of important number series questions which are fully solved for your convenience, don’t forget to practice this chapter for your exams.

## (01) Find the missing number in a sequence2, 12, 30, ?, 90, 132

Options:
a. 48
b. 56
c. 63
d. 72

STEP 1:
Lets find the difference of first and second number then second and third number and so on by selecting options one by one.

Now first we select option 48 and observe how the sequence formation taking place

Here we don’t find any particular series so now forming difference of difference number to see whether any form of sequence is forming or not.

Step 2:
Check the sequence with option b (number 56)

## (02) Find the pattern in number and write the missing sequence10, 100, 200, 310, ?

Options:
a. 400
b. 410
c. 420
d. 430

Step 01
Lets  find the difference of first and second number then second and third number and so on, by difference of difference method

Now we select an option such that when subtract to 310 it gives 120

Here we find 430 is only option which gives our required series

## (03) Find the missing number in the sequence0.5, 2, 4.5, 8, 12.5, ?

a. 16
b. 17
c. 16.5
d. 18

Step 1
Lets  find the difference of first and second number then second and third number and so on, by difference of difference method.

Here we get a increasing order of +1  series . Now we select an option such that when subtract to 12.5 it gives 5.5

Step 2

## (04) Find the missing number in the sequence2, 15, 41, 80, ?

Options:
a. 120
b. 121
c. 132
d. 111

Step 1:
Lets  find the difference of first and second number then second and third number and so on, by difference of difference method

Here we get an increasing order of +13  series
Now we select an option such that when subtract to 80  it gives 52.

Step 02
Let the right answer be x
x – 80 = 52
x = 80+52
x = 132

## (05) Find the missing number in the sequence109, 74, 46, 25, 11, ?

Options:
a. 3
b. 0
c. 11
d. 4

Step 01
Lets  find the difference of first and second number then second and third number and so on, by difference of difference method

Here we get a decreasing  order of -7  series .
Now we select an option such that when subtract to 11  it gives -7

Step 02

## (06) Find the missing number in the sequence          3, 20, 63, 144, 275, ?

Options
(a) 554
(b) 548
(c) 468
(d) 354

Step 01
Lets  find the difference of first and second number then second and third number and so on

Here we don’t find any particular series, so by applying difference of difference method

Here we get a increasing order of +12 series . The question is solved step by step as given below

Hence, 468 is the right answer

## (07) Find the missing number in the sequence18, 24, 21, 27, ?, 30

Options
(a) 33
(b) 30
(c) 24
(d) 21

Here if we find the difference of difference we don’t get any particular series so here taking alternate difference

We can see that alternate number differ by number 3
we get upper series of +3 so it is obvious that our lower series should be of +3, so selecting such an option that we get required series of +3

Here we find 24 is only option which gives our required series

## (08) Find the missing number in the sequence3, 8, 19, 36, 59, 90, ?

a. 121
b. 131
c. 127
d. 136

Solution- Let’s find the difference of first and second number then second and third number and so on

Here we get an alternate prime number series
So the required number when subtracted from 90 gives next alternate prime number that is 41

Let the required number be x
x – 90 = 41
x = 41 + 90
x = 131

Hence 131 is the right answer

## (09) Find the missing number in the series

a. 6/11
b. 5/9
c. 9/11
d. 7/13

Here we take difference of first two element and last two element

We find here that lower difference is just double the upper difference
So now we select an option such that it gives same result as above

Here we find 7/13 is only option which gives our required series