Series Definition, Types, Formulas and Examples

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What is Series Called

Such a sequence of Numbers or letters, which proceed in a certain order, is called a series.

In the questions asked under this, a series of some numbers or letters is given in which one space is left blank (?) or some number or letter is given like this.

Which does not follow the rule according to which other numbers/letters in the series are arranged, you have to choose the number/letter which comes in place of the same blank space (?) or that number/letter from the answer options.

Apart from those who do not follow that rule, questions from provisional number are also asked in this chapter.

Point#1 – Following information is required to identify the missing/wrong term of a series based on numbers.

1. If there is not much difference between the first and last term of the number series and the series is visible in ascending form, then the series can be based on ‘addition’.
2. If there is not much difference between the first and last term of the number series and the series appears to be in ascending form, then the series can be based on ‘subtraction‘.
3. If the difference between the first and last term of a number series is very large, then the series can be based on multiplication or Multiplication and subtraction or multiplication and addition.
4. If the difference between the last two terms of a number series is very small compared to the first two terms, then the series can be based on the addition or difference of squared/cubed numbers.

Point #2 – To identify the missing/wrong term of a series based on letters, it is necessary to have the following information about the serial position of the letters of the English alphabet.

While filling the vacant posts under the continuous series, remember that the two/three/four/five… posts of the series should be arranged according to some logical rule.

Series Related Questions and Answers

1. Which number from the four options given below will come in place of the question mark (?) in the following series of numbers?

512, 256, 128, 64, 32 ?

A. 8
B. 16
C. 60
D. 32

Ans. 16

2. 4, 8, 28, 80, 244, ?

A. 728
B. 428
C. 628
D. 278

Ans. 728

3. 1, 3, 3, 6, 7, 9, ? , 12, 21

A. 10
B. 11
C. 12
D. 13

Ans. 13

4. 6, 12, 21, ?, 48

A. 33
B. 38
C. 40
D. 45

Ans. 33

5. 36, 34, 30, 28, 24, ?

A. 20
B. 22
C. 23
D. 26

Ans. 22

6. 7, 10, 8, 11, 9, 12, ?

A. 7
B. 10
C. 12
D. 13

Ans. 10

7. Find out (?) which of the following?

6, 13, 25, 51, 101, ?

A. 201
B. 202
C. 203
D. 205

Ans. 203

8. Find out (?) which of the following?

A. 27
B. 35
C. 45
D. 56

Ans. 35

9. Find out (?) which of the following?

A. 18
B. 27
C. 36
D. 81

Ans. 27

10. Which number from the four options given below will come in place of the question mark (?) in the following series of numbers?

4832, 5840, 6848, ?

A. 7815
B. 7846
C. 7856
D. 7887

Ans. 7856

11. Which letter will come in place of the question mark (?) in the following series of letters?

BMX, DNW, FOU, ?

A. GHO
B. GPS
C. HPS
D. HPT

Ans. HPT

12. A, D, H, M, ? , Z

A. T
B. S
C. N
D. G

Ans. S

13. A, G, L, P, S, ?

A. U
B. W
C. X
D. Y

Ans. U

14. Which letter will come in place of the question mark (?) in the following series of letters?

A, D, G, J, M, P ?

A. Q
B. R
C. S
D. T

Ans. S

15. WFB, TGD, QHG, ?

A. NIJ
B. NIK
C. NJK
D. OIK

Ans. NIK

16. AI, BJ, Ck, ?

A. GH
B. DM
C. DL
D. LM

Ans. DL

17. Z, U, Q, ? , L

A. L
B. K
C. M
D. N

Ans. N

18. Fill it with the correct set of letters?

MOQ, NPR, OQS,……………..

A. PTR
B. PRT
C. QSU
D. PTT

Ans. PRT

19. AYD, BVF, DRH, ? ,  KGL

A. FMI
B. GMJ
C.  GLJ
D. HLK

Ans. FMI

20. One term in the following number series is wrong, find that wrong term?

Z, W, S, P, L, I, E, ?

A. B
B. D
C. F
D. K

Ans. B

21. One term in the following number series is wrong, find that wrong term?

7, 9, 17, 42, 91, 172

A. 17
B. 42
C. 9
D. 91

Ans. 9

22. Which series of numbers from the options are wrong?

1, 8, 27, 65, 125, 216

A. 65
B. 216
C. 125
D. 27

Ans. 65

23. Find the number which does not fit in the following number series?

291, 170, 121, 40, 15, 6, 5

A. 291
B. 170
C. 121
D. 40

Ans. 170

24. Name the odd number in this series?

1, 3, 7, 11, 15, 18, 21

A. 3
B. 7
C. 18
D. 21

Ans. 18

25. Find the correct alphabetical order of the missing letters of the following letter series from the options given below?

w-uww–w-xuw

A. xuxw
B. xxwu
C. xxuw
D. xxww

Ans. xxuw (wXuwwXUwWxuw)

26. Which of the following options will show the meaningful order of the words given below?

1. Family 2. Community 3. Member 4. Area 5. Country

A. 3, 1, 4, 2, 5
B. 1, 2, 4, 5
C. 3, 1, 2, 5, 4
D. 3, 1, 4, 5, 2

Ans. 3, 1, 2, 4, 5 (Member, Family, Community, Area, Country)

27. Which of the following letter sets will complete the given letter series when placed sequentially in the blank spaces?

a_aaaba__ba_ab

A. abaaaa
B. abaaba
C. aababa
D. ababaa

Ans. abaaaa

28. ?, PSVYB, EHKNQ, TWZCF, ILORU

A. BEHKN
B. ADGJM
C. SVYBE
D. ZCFIL

Ans. ADGJM

Read More :
Mathematical Operations	Seating Arrangement Questions
Blood Relations	English Alphabet and Vocabulary Test

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