Practice Number Series questions covering missing term, wrong term, and series-completion patterns (arithmetic, geometric, and mixed sequences) for Logical Reasoning.
Question 1
Look at this series: 70, 66, 59, 55, 48, ... What number should come next?
A
41✓✗
B
44✓✗
C
42✓✗
D
45✓✗
Explanation
This is a simple alternating subtraction series, which subtracts 4, then 7: 48 - 4 = 44.
Question 2
Look at this series: 4, 12, 4, 17, 4, ... What number should come next?
A
21✓✗
B
27✓✗
C
17✓✗
D
22✓✗
Explanation
This is a simple addition series with a random number, 4, interpolated as every other number. In the series, 5 is added to each number except 4, to arrive at the next number: 12, 17, 22.
Question 3
Look at this series: 5, 7, 12, 14, 19, 21, ... What number should come next?
A
24✓✗
B
23✓✗
C
26✓✗
D
28✓✗
Explanation
This alternating addition series begins with 5; then 2 is added to give 7; then 5 is added to give 12; then 2 is added, and so on: 21 + 5 = 26.
Question 4
Look at this series: 95, 87, 79, 71, 63, ... What number should come next?
A
55✓✗
B
53✓✗
C
57✓✗
D
47✓✗
Explanation
This is a simple subtraction series. Each number is 8 less than the previous number: 63 - 8 = 55.
Question 5
Look at this series: 17, 4, 17, 7, 17, 10, 17, ... What number should come next?
A
12✓✗
B
14✓✗
C
17✓✗
D
13✓✗
Explanation
In this alternating repetition series, the number 17 is interpolated every other number into an otherwise simple addition series that increases by 3, beginning with the number 4: 4, 7, 10, 13.
Question 6
Look at this series: 90, 90, 78, 78, 66, 66, ... What number should come next?
A
66✓✗
B
54✓✗
C
52✓✗
D
42✓✗
Explanation
In this series, each number is repeated, then 12 is subtracted to arrive at the next number: 66 - 12 = 54.
Question 7
Look at this series: 30, 28, 31, 29, 32, 30, ... What number should come next?
A
31✓✗
B
32✓✗
C
33✓✗
D
34✓✗
Explanation
In this alternating subtraction and addition series, 2 is subtracted, then 3 is added, and so on: 30 + 3 = 33.
Question 8
Look at this series: 50, 47, 41, 38, 32, ... What number should come next?
A
29✓✗
B
26✓✗
C
28✓✗
D
24✓✗
Explanation
This is an alternating number subtraction series. First, 3 is subtracted, then 6, then 3, and so on: 32 - 3 = 29.
Question 9
Look at this series: 5, 9, 7, 11, 9, 13, ... What number should come next?
A
9✓✗
B
13✓✗
C
15✓✗
D
11✓✗
Explanation
This is a simple alternating addition and subtraction series. In the first pattern, 4 is added; in the second, 2 is subtracted: 5, 9, 7, 11, 9, 13, 11.
Question 10
Look at this series: 3, 1, (1/3), (1/9), ... What number should come next?
A
(1/12)✓✗
B
(1/27)✓✗
C
(1/18)✓✗
D
(1/6)✓✗
Explanation
This is a simple division series; each number is one-third of the previous number: (1/9) / 3 = (1/27).
Question 11
Look at this series: 6, 50, 10, 47, __, 44, 18, ... What number should fill the blank?
A
12✓✗
B
44✓✗
C
14✓✗
D
16✓✗
Explanation
This is an alternating series. The first series begins with 6 and adds 4 (6, 10, 14, 18); the second begins with 50 and subtracts 3 (50, 47, 44). The blank is 14.
Question 12
Look at this series: 40, 51, 55, 40, 59, __, 40, 67, ... What number should fill the blank?
A
61✓✗
B
63✓✗
C
40✓✗
D
67✓✗
Explanation
In this series, 4 is added to the previous number; the number 40 is inserted as every third number: 51, 55, 59, 63, 67. The blank is 63.
Question 13
Look at this series: III, VII, XI, XV, __, XXIII, ... What number should fill the blank?
A
XVIII✓✗
B
XXI✓✗
C
XVII✓✗
D
XIX✓✗
Explanation
This is a simple addition series of Roman numerals; each number is 4 more than the previous number: 3, 7, 11, 15, 19, 23. The blank is XIX.
Question 14
Look at this series: 724, 362, 372, 186, ____, 98, ... What number should fill the blank?
A
196✓✗
B
176✓✗
C
206✓✗
D
190✓✗
Explanation
This is an alternating division and addition series: first divide by 2, then add 10. 372 / 2 = 186, 186 + 10 = 196, 196 / 2 = 98.
Question 15
Look at this series: H5, __, F20, E40, D80, ... What number should fill the blank?
A
G20✓✗
B
F10✓✗
C
G10✓✗
D
H10✓✗
Explanation
The letters decrease by 1 and the numbers are multiplied by 2: H5, G10, F20, E40, D80.
Question 16
Choose the correct alternative that will continue the same pattern and fill in the blank space. 7, 17.5, 61.25, _____
A
264.65✓✗
B
275.625✓✗
C
374.65✓✗
D
375.625✓✗
Explanation
Each term is multiplied by 2.5, then 3.5, then 4.5: 7 x 2.5 = 17.5, 17.5 x 3.5 = 61.25 and 61.25 x 4.5 = 275.625.
Question 17
How many 8's are present in the following sequence of numbers which are exactly divisible by both its preceding and following numbers ?

3 8 6 8 8 7 6 8 3 4 8 2 5 6 2 8 2 4 8 6 3 7 4 8 4 5 8 4
A
5✓✗
B
6✓✗
C
2✓✗
D
Less than 4✓✗
Explanation
An 8 qualifies only if it is exactly divisible by both its neighbours. Checking each 8: 3-8-6 no, 6-8-8 no, 8-8-7 no, 6-8-3 no, 4-8-2 yes, 2-8-2 yes, 4-8-6 no, 4-8-4 yes, 5-8-4 no.
So 3 eights qualify, which is fewer than 4.
Question 18
How many 7's are present in the following sequence of numbers which are both preceded and followed by perfect square numbers ?

8 6 3 7 9 7 4 3 6 9 7 2 1 7 4 9 5 2 5 4 7 9 5 2 9 7 1 4 7 1
A
4✓✗
B
2✓✗
C
5✓✗
D
3✓✗
Explanation
A 7 qualifies only when both neighbours are perfect squares (0, 1, 4 or 9). Checking each 7 by its neighbours: 3-7-9 no, 9-7-4 yes, 9-7-2 no, 1-7-4 yes, 4-7-9 yes, 9-7-1 yes, 4-7-1 yes.
So 5 sevens qualify.
Question 19
How many 9's are present in the following sequence of numbers which are preceded by 5 but not followed by 7?

5 9 6 8 2 8 8 5 9 7 5 3 9 8 5 9 4 7 3 8 5 9 4 8 9 0 6 5 9 3 8 0 2
A
5✓✗
B
3✓✗
C
4✓✗
D
More than 4✓✗
Explanation
The 9s that are preceded by 5 are followed by 6, 7, 4, 4 and 3 in turn (5 in all).
Excluding the one followed by 7 leaves 4.
Question 20
Choose the correct alternative that will continue the same pattern and fill in the blank space. 56, 132, 240, 380, _____
A
430✓✗
B
530✓✗
C
630✓✗
D
552✓✗
Explanation
The differences are 76, 108 and 140, which increase by 32 each time. The next difference is 172.
So the next term = 380 + 172 = 552.
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