Series Completion QA || Reasoning

By

 Series Completion Questions and Answers

Q1: Find the Missing Number

2, 5, 10, 17, 26, (...)

Options:
A) 37
B) 38
C) 39
D) 40

Answer: A) 37

Explanation:
Each term is obtained by adding consecutive odd numbers starting from 1. The pattern is:

  • 2 + 3 = 5

  • 5 + 5 = 10

  • 10 + 7 = 17

  • 17 + 9 = 26

  • 26 + 11 = 37

Q2: Find the Missing Number

144, 121, 100, 81, 64, (...)

Options:
A) 50
B) 49
C) 36
D) 25

Answer: B) 49

Explanation:
Each term is the square of consecutive descending numbers:

  • 12² = 144

  • 11² = 121

  • 10² = 100

  • 9² = 81

  • 8² = 64

  • 7² = 49

Q3: Find the Missing Number

6, 11, 21, 36, 56, (.....)

Options:
A) 41
B) 51
C) 61
D) 81

Answer: D) 81

Explanation:
The pattern follows:

  • +5, +10, +15, +20, +25

  • 6 + 5 = 11

  • 11 + 10 = 21

  • 21 + 15 = 36

  • 36 + 20 = 56

  • 56 + 25 = 81

Q4: Find the Missing Number

3, 7, 15, 31, 63, (.......)

Options:
A) 92
B) 115
C) 117
D) 127

Answer: D) 127

Explanation:
Each term follows the pattern:

  • (Previous term × 2) + 1

  • (3 × 2) + 1 = 7

  • (7 × 2) + 1 = 15

  • (15 × 2) + 1 = 31

  • (31 × 2) + 1 = 63

  • (63 × 2) + 1 = 127

Q5: Find the Missing Number

1, 2, 6, 24, (....)

Options:
A) 150
B) 120
C) 95
D) 60

Answer: B) 120

Explanation:
Each term follows:

  • Multiply by the position number

  • 1 × 1 = 1

  • 1 × 2 = 2

  • 2 × 3 = 6

  • 6 × 4 = 24

  • 24 × 5 = 120

Q6: Find the Missing Number

2, 5, 9, 19, 37, (...).

Options:
A) 72
B) 74
C) 75
D) 76

Answer: C) 75

Explanation:
Each term follows the alternating pattern:

  • ×2 + 1, ×2 − 1, ×2 + 1, ×2 − 1

  • 2 × 2 + 1 = 5

  • 5 × 2 − 1 = 9

  • 9 × 2 + 1 = 19

  • 19 × 2 − 1 = 37

  • 37 × 2 + 1 = 75

Q7: Find the Missing Number

34, 18, 10, 6, 4, (.....)

Options:
A) 4
B) 1
C) 2
D) 3

Answer: D) 3

Explanation:
Each term follows:

  • ÷2 and then +1

  • 34 ÷ 2 + 1 = 18

  • 18 ÷ 2 + 1 = 10

  • 10 ÷ 2 + 1 = 6

  • 6 ÷ 2 + 1 = 4

  • 4 ÷ 2 + 1 = 3

Q8: Find the Missing Number

1, 4, 2, 8, 6, 24, 22, 88, (......)

Options:
A) 352
B) 154
C) 90
D) 86

Answer: D) 86

Explanation:
Pattern follows:

  • ×4, −2, ×4, −2...

  • 1 × 4 = 4

  • 4 − 2 = 2

  • 2 × 4 = 8

  • 8 − 2 = 6

  • 6 × 4 = 24

  • 24 − 2 = 22

  • 22 × 4 = 88

  • 88 − 2 = 86

Q9: Find the Missing Number

840, 168, 42, 14, (....)

Options:
A) 1
B) 5
C) 7
D) 9

Answer: C) 7

Explanation:
Each term is divided by consecutive descending numbers:

  • 840 ÷ 5 = 168

  • 168 ÷ 4 = 42

  • 42 ÷ 3 = 14

  • 14 ÷ 2 = 7

Q10: Find the Missing Number

3, 8, 22, 63, 185, (....)

Options:
A) 285
B) 295
C) 310
D) 550

Answer: D) 550

Explanation:
The pattern follows:

  • ×3 − 1, ×3 − 2, ×3 − 3, ×3 − 4

  • (3 × 3) − 1 = 8

  • (8 × 3) − 2 = 22

  • (22 × 3) − 3 = 63

  • (63 × 3) − 4 = 185

  • (185 × 3) − 5 = 550


Q11

Sequence: 462, 420, 380, (...), 306
Options:
A) 352
B) 342
C) 332
D) 322

Answer: 342
Explanation: The pattern follows a decreasing sequence where each term is obtained by subtracting the next even number in the sequence: -42, -40, -38, -36...
Missing term = 380 - 38 = 342

Q12

Sequence: 120, 99, 80, 63, 48, (...)
Options:
A) 35
B) 38
C) 39
D) 40

Answer: 35
Explanation: The pattern follows a decreasing sequence by subtracting consecutive odd numbers: -21, -19, -17, -15...
Missing term = 48 - 13 = 35

Q13

Sequence: 3, 10, 101, (...)
Options:
A) 10101
B) 10201
C) 10202
D) 11012

Answer: 10202
Explanation: Each term is obtained by squaring the previous term and adding 1.
Missing term = (101)^2 + 1 = 10202

Q14

Sequence: 2, 6, 18, 54, (...) (Find the 8th term)
Options:
A) 4370
B) 4374
C) 7443
D) 7434

Answer: 4374
Explanation: This sequence follows a geometric progression (G.P.) with a common ratio of 3.
Formula: nth term = a × r^(n-1)
8th term = 2 × 3^(8-1) = 2 × 2187 = 4374

Q15

Sequence: 125, 80, 45, 20, (?)
Options:
A) 5
B) 8
C) 10
D) 12

Answer: 5
Explanation: The pattern follows a decreasing sequence where each term is obtained by subtracting reducing values: -45, -35, -25, -15...
Missing term = 20 - 15 = 5

Q16

Sequence: 1, 1, 4, 8, 9, 27, 16, (?)
Options:
A) 32
B) 64
C) 81
D) 256

Answer: 64
Explanation: The pattern alternates between squares and cubes of consecutive natural numbers:
1^2, 1^3, 2^2, 2^3, 3^2, 3^3, 4^2...
Missing term = 4^3 = 64

Q17

Sequence: 1, 2, 3, 6, 9, 18, (?), 54
Options:
A) 18
B) 27
C) 36
D) 81

Answer: 27
Explanation: The pattern alternates between multiplying by 2 and 3.
Missing term = 18 × (3) = 27

Q18

Sequence: 6, 13, 25, 51, 101, (?)
Options:
A) 201
B) 202
C) 203
D) 205

Answer: 203
Explanation: The pattern follows doubling and adding 1:
Missing term = 101 × 2 + 1 = 203

Q19

Sequence: 5, 6, 9, 15, (?), 40
Options:
A) 21
B) 25
C) 27
D) 33

Answer: 25
Explanation: Each term is obtained by adding consecutive triangular numbers: 1, 3, 6, 10...
Missing term = 15 + 10 = 25

Question 20

Find the missing number in the sequence:

1, 3, 4, 8, 15, 27, ?

Options:
A) 37
B) 44
C) 50
D) 55

Answer: 50

Explanation:

The given series follows a pattern where each term is obtained by summing the previous three terms.

  1. 1 + 3 + 4 = 8
  2. 3 + 4 + 8 = 15
  3. 4 + 8 + 15 = 27
  4. 8 + 15 + 27 = 50

Thus, the missing term is 50.

Question 21

Find the missing number in the sequence:

3, 4, 7, 7, 13, 13, 21, 22, 31, 34, ?

Options:
A) 42
B) 37
C) 51
D) 52

Answer: 37

Explanation:

The sequence consists of two interleaved series:

  • First series: 3, 7, 13, 21, 31 → increases by 4 each time.
  • Second series: 4, 7, 13, 22, 34 → follows an alternating pattern of +3, +6.

Following this pattern:

  • The next term in the second series after 34 is 34 + 3 = 37.

Thus, the missing term is 37.

Comments

Post a Comment