UPSC CSE Prelims CSAT (Paper II) previous year questions on Sequence and Series (Quantitative Ability), asked from 2011–2026, with answers. There are 53 questions in this post. Attempt each question, then click Show Answer to check.
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1] A pattern formed by two characters a and b is repeated more than once in the following string:
× b × a × a × × a × a × bab
What is × × in the 7th and 8th positions from the left in the above string? [2026/18]
(a) aa
(b) ab
(c) ba
(d) bb
Show Answer
Ans: (d) bb
2] In a sequence of numbers, each number other than the first two is the sum of the two immediately preceding numbers from it. If the first two numbers in the sequence are 4 and 7, then the sixth number is [2026/57]
(a) 29
(b) 37
(c) 43
(d) 47
Show Answer
Ans: (d) 47
3] What comes at X and Y respectively in the following sequence?
January, January, December, October, X, March, October, Y, September [2025/8]
(a) July, May
(b) July, April
(c) June, May
(d) June, April
Show Answer
Ans: (b) July, April
4] Consider the sequence AB_CC_A_BCCC_BBC_C that follows a certain pattern. Which one of the following completes the sequence? [2025/30]
(a) B, C, B, C, A
(b) A, C, B, C, A
(c) B, C, B, A, C
(d) C, B, B, A, C
Show Answer
Ans: (c) B, C, B, A, C
5] What is X in the sequence 24, X, 12, 18, 36, 90? [2025/36]
(a) 18
(b) 12
(c) 9
(d) 6
Show Answer
Ans: (b) 12
6] What is X in the sequence 1, 3, 6, 11, 18, X, 42? [2025/60]
(a) 26
(b) 27
(c) 29
(d) 30
Show Answer
Ans: (c) 29
7] Consider the sequence A _ BCD _ BBCDABC _ DABC _ D that follows a certain pattern. Which one of the following completes the sequence? [2024/24]
(a) B, A D, C
(b) B, A, C, D
(c) A, A, C, D
(d) A, A, D, C
Show Answer
Ans: (c) A, A, C, D
8] What is the sum of the first 28 terms in the following sequence? [2024/46]
1,1,2,1,3,2,1,4,3,2,1,5,4,3,2, …
(a) 83
(b) 84
(c) 85
(d) 86
Show Answer
Ans: (b) 84
9] What will come in place of * in the sequence 3, 14, 39, 84, *, 258? [2024/79]
(a) 150
(b) 155
(c) 160
(d) 176
Show Answer
Ans: (b) 155
10] Choose the group which is different from the others: [2023/40]
(a) 17, 37, 47, 97
(b) 31, 41, 53, 67
(c) 71, 73, 79, 83
(d) 83, 89, 91, 97
Show Answer
Ans: (d) 83, 89, 91, 97
11] What is the middle term of the sequence Z, Z, Y, Y, Y, X, X, X, X, W, W, W, W, W….., A? [2023/55]
(a) H
(b) I
(c) J
(d) M
Show Answer
Ans: (b) I
12] Consider the sequence
ABC_ _ ABC _ DABBCD_ ABCD
that follows a certain pattern.
Which one of the following completes the sequence? [2023/75]
(a) DACB
(b) CDAB
(c) DCCA
(d) DDCA
Show Answer
Ans: (d) DDCA
13] The letters of the word “INCOMPREHENSIBILITIES” are arranged alphabetically in reverse order. How many positions of the letter/letters will remain unchanged? [2023/80]
(a) None
(b) One
(c) Two
(d) Three
Show Answer
Ans: (c) Two
14] What is the value of X in the sequence 20, 10, 10, 15, 30, 75, X? [2022/4]
(a) 105
(b) 120
(c) 150
(d) 225
Show Answer
Ans: (d) 225
15] If the order of the letters in the English alphabet is reversed and each letter represents the letter whose position it occupies, then which one of the following represents ‘LUCKNOW’? [2022/16]
(a) OGXPMLD
(b) OGXQMLE
(c) OFXPMLE
(d) OFXPMLD
Show Answer
Ans: (d) OFXPMLD
16] In the series AABABCABCDABCDE…. which letter appears at the 100th place? [2022/29]
(a) G
(b) H
(c) I
(d) J
Show Answer
Ans: (c) I
17] What is the value of X in the sequence 2, 12, 36, 80, 150, X? [2022/75]
(a) 248
(b) 252
(c) 258
(d) 262
Show Answer
Ans: (b) 252
18] Replace the incorrect term by the correct term in the given sequence 3, 2, 7, 4, 13, 10, 21, 18, 31, 28, 43, 40 where odd tents and even terms follow the same pattern [2021/26]
(a) 0
(b) 1
(c) 3
(d) 6
Show Answer
Ans: (a) 0
19] Following is a matrix of certain entries. The entries follow a certain trend row-wise. Choose the missing entry (?) accordingly. [2021/27]
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(a) 9B
(b) 3A
(c) 3B
(d) 3C
Show Answer
Ans: (c) 3B
20] You are given two identical sequences in two rows:
What is the entry in the place of C for the Sequence-II? [2021/28]
(a) 2.5
(b) 5
(c) 9.375
(d) 32.8125
Show Answer
Ans: (c) 9.375
21] In the series _b_a_ba_b_abab_aab; fill in the six blanks ( _ ) using one of the following given four choices such that the series follows a specific order. [2021/65]
(a) bababa
(b) baabba
(c) bbaabb
(d) ababab
Show Answer
Ans: (d) ababab
22] In the English alphabet, the first 4 letters are written in opposite order; and the next 4 letters are written in opposite order and so on; and at the end Y and Z are interchanged. Which will be the fourth letter to the right of the 13th letter? [2021/40]
(a) N
(b) T
(c) H
(d) I
Show Answer
Ans: (b) T
23] A simple mathematical operation in each number of the sequence 14, 18, 20, 24, 30, 32, ….. results in a sequence with respect to prime numbers. Which one of the following is the next number in the sequence? [2020/13]
(a) 34
(b) 36
(c) 38
(d) 40
Show Answer
Ans: (c) 38
24] Consider the following arrangement that has some missing letters:
abab_b_bcb_dcdcded_d The missing letters which complete the arrangement are [2020/15]
(a) a, b, c, d
(b) a, b, d, e
(c) a, c, c, e
(d) b, c, d, e
Show Answer
Ans: (c) a, c, c, e
25] Consider the following sequence of numbers:
5 1 4 7 3 9 8 5 7 2 6 3 1 5 8 6 3 8 5 2 2 4 3 4 9 6
How many odd numbers are followed by the odd number in the above sequence? [2020/34]
(a) 5
(b) 6
(c) 7
(d) 8
Show Answer
Ans: (b) 6
26] What is x in the sequence 132, 129, 124, 117, 106, 93, X ? [2019/48]
(a) 74
(b) 75
(c) 76
(d) 77
Show Answer
Ans: (c) 76
27] What is x in the sequence 4, 196, 16, 144, 36, 100, 64, X ? [2019/51]
(a) 48
(b) 64
(c) 125
(d) 256
Show Answer
Ans: (b) 64
28] Consider the following sequence that follows some arrangement:
c_accaa_aa_bc_b
The letters that appear in the gaps are[2019/54]
(a) abba
(b) cbbb
(c) bbbb
(d) cccc
Show Answer
Ans: (b) cbbb
29] If every alternative letter of the English alphabet from B onwards (including B) is written in lower case (small letters) and the remaining letters are capitalized, then how is the first month of the second half of the year written? [2019/68]
(a) JuLY
(b) jULy
(c) jUly
(d) jUlY
Show Answer
Ans: (d) jUlY
30] In the sequence 1, 5, 7, 3, 5, 7, 4, 3, 5, 7, how many such 5s are there which are not immediately preceded by 3 but are immediately followed by 7? [2019/70]
(a) 1
(b) 2
(c) 3
(d) None
Show Answer
Ans: (a) 1
31] Consider the following pattern of numbers:
What is the number at? in the above pattern? [2018/3]
(a) 17
(b) 19
(c) 21
(d) 23
Show Answer
Ans: (a) 17
32] How many diagonals can be drawn by joining the vertices of an octagon? [2018/4]
(a) 20
(b) 24
(c) 28
(d) 64
Show Answer
Ans: (a) 20
33] Consider the figures given below:
To fit the question, mark the correct answer is [2018/66]
(a) 
(b) 
(c) 
(d) 
Show Answer
Ans: (a)
34] Consider the following figures:
In the figures (I) to (VI) above, some parts are shown to change their positions in regular directions. Following the same sequence, which of the figures given below will appear at (VII) stage? [2018/70]
Show Answer
Ans: (b)
35] Consider the sequence given below:
4/12/95, 1/1/96, 29/1/96, 26/2/96, ….
What is the next term of the series? [2018/59]
(a) 24/3/96
(b) 25/3/96
(c) 26/3/96
(d) 27/3/96
Show Answer
Ans: (b) 25/3/96
36] Consider the figures given below:
To fit the question mark, the correct answer is [2015/11]
Show Answer
Ans: (a)
37] Consider the following matrix:
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What is missing number at ‘?’ in the matrix? [2015/12]
(a) 5
(b) 0
(c) 7
(d) 3
Show Answer
Ans: (a) 5
38] What is the missing number X of the series 7, X, 21, 31, 43, ? [2015/13]
(a) 11
(b) 12
(c) 13
(d) 14
Show Answer
Ans: (c) 13
39] Examine the following figure:
Which one of the following figures has the above figure embedded in it? [2014/39]
Show Answer
Ans: (c)
40] Consider the following matrix:
Which one of the following figures fits into the blank part of the above matrix? [2014/40]
Show Answer
Ans: (b)
41] Consider the table given below in which the numbers bear certain relationship among themselves along the rows:
Which one of the following numbers is the missing number indicated above by X? [2014/42]
(a) 19
(b) 15
(c) 14
(d) 8
Show Answer
Ans: (bd)
42] Consider the following matrix with one empty block in the lower extreme corner:
Which of the following figures could fit in the empty block and thus complete the matrix? [2014/43]
Show Answer
Ans: (a)
43] Consider the following figures:
Change in positions of beads in the four figures above follows a sequence. Following the same sequence, which of the figures below should appear as the fifth figure above? [2014/45]
Show Answer
Ans: (b)
44] The letters L, M, N, O, P, Q, R, S and T in their order are substituted by nine integers 1 to 9 but not in that order. 4 is assigned to P. difference between P and T is 5, The difference between N and T is 3. What is the integer assigned to N? [2014/61]
(a) 7
(b) 5
(c) 4
(d) 6
Show Answer
Ans: (d) 6
45] Consider the following figures 1,2,3 and 4.
In the figures from 1 to 4 above, two symbols are shown to change their position in a regular direction. Following the same sequence, which one of the following will appear at the fifth stage? [2013/44]
Directions for the following 2 (two) items :
In each item, there are two sets of figures; first four figures named Problem figures and next four figures named Answer figures indicated as (a). (c) and (d), The problem figures follow a particular sequence. In accordance with the same, which one of the four answer figures should appear as the fifth figure?
Show Answer
Ans: (b)
46] Problem Figures: [2013/45]
Answer Figures:
Show Answer
Ans: (c)
47] Problem Figure: [2013/46]
Answer figures
Show Answer
Ans: (b)
48] Consider the following matrix
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What is the number at ‘X’ in the above matrix? [2013/48]
(a) 5
(b) 8
(c) 9
(d) 11
Show Answer
Ans: (c) 9
49] Examine the following three figures in which the number follow a specific pattern:
The missing number in the third figure above is? [2013/50]
(a) 7
(b) 16
(c) 21
(d) 28
Show Answer
Ans: (b) 16
50] Consider the following figures:
Which one of the following figures would logically come in the 7th position indicated above by a question mark? [2013/57]
Show Answer
Ans: (d)
51] The elements of the problem figures given below are changing with certain rules as we observe them from left to right:
According to this rule which of the following would be the next figure if the changes were made in the same rule? [2012/45]
Show Answer
Ans: (d)
52] Figures
Which one of the figures shown below occupies the blank space(?) in the matrix given above? [2012/50]
Show Answer
Ans: (d)
53] Consider the following figures:
What is the missing number? [2011/24]
(a) 7
(b) 8
(c) 9
(d) 10
Show Answer
Ans: (c) 9
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