Sequence and Series Questions & Solutions : Reasoning

• Which number would replace underline mark in the series?

2, 5, 10, 17, ---, 37  A.) 27 B.) 24 C.) 26 D.) 28

Here the difference between the consecutive terms is increase by 2

5 - 2 = 3,

10 - 5 = 5,

17 - 10 = 7,

then 17 + 9 = 26.

• Which number would replace underline mark in the series?

1, 6, 26,_____, 426.  A.) 86 B.) 76 C.) 106 D.) 96

Here the difference between the consecutive terms is multiplied by 4.

The difference of the two consecutive numbers is 5, 20, .....

5 × 4 = 20

20 × 4 = 80

26 + 80 = 106.

• Which number would replace underline mark in the series?

1, 20, 58, ____, 191.  A.) 105 B.) 115 C.) 111 D.) 116

Here the difference between the two consecutive terms is 19, 38, 57, 76

58 + 57 = 115

• 2, 10, 40, 120,____  A.) 240 B.) 360 C.) 470 D.) 210

Here the series is a multiplication series.

The order of the multiplication is ×5, ×4, ×3, ×2

120 × 2 = 240

• 3, 9, 21, ___, 93  A.) 36 B.) 45 C.) 47 D.) 51

First difference is 6 and second is 12.

But if we take third as 18, then fourth difference will be 24.

Then 93 can not be the last term.

So we have to take the difference as 6, 12, 24 and 48.

So 21 + 24 = 45.

• 18 21 25 18 29 33 18

What numbers should come next ?  A.) 43 18 B.) 41 44 C.) 37 41 D.) 38 41

This is a simple addition series with a random number, 18, interpolated as every third number.

In the series, 4 is added to each number except 18, to arrive at the next number.

• 20 20 17 17 14 14 11 What numbers should come next ?

 A.) 8 8 B.) 8 9 C.) 11 8 D.) 8 9s

This is a simple subtraction with repetition series.

It begins with 20, which is repeated, then 3 is subtracted, resulting in 17, which is repeated, and so on.

Rule = (1st no) (1st no) (1st no - 3 = 2nd no) (2nd no repeat) (2nd no - 3 = 3rd no) (3rd no repeat). . .

Now (20) (20) (20 - 3 = 17) (17) (17 - 3 = 14) (14) (14 - 3 = 11) (11) (11 - 3 = 8) (8)

So the answer is e = 11 8.

• 3 13 18 23 28 33

What number should come next?  A.) 38 43 B.) 37 42 C.) 38 44 D.) 39 44

In this simple addition series, each number is 5 greater than the previous number.

Rule = (1st no) (1st no + 5 = 2nd no) (2nd no + 5 = 3rd no) . . .

Now (3) (3 + 5 = 8) (8 + 5 = 13) (13 + 5 = 18) (18 + 5 = 23) (23 + 5 = 28) (28 + 5 = 33) (33 + 5 = 38) (38 + 5 = 43)

So the answer is c = 38 43

• Look at this series: 1000, 200, 40, . . .

What number should come next?  A.) 10 B.) 8 C.) 9 D.) 12

This is a simple division series.

Each number is divided by 5.

Rule = (1st number / 5 = 2nd number) (2nd number / 5 = 3rd number)....

Now, (1000 / 5 = 200), (200 / 5 = 40), (40 / 5 = 8)...

So answer is a = 8.

• Look at this series: 7, 10, 8, 11, 9, 12, . . .

What number should come next?  A.) 7 B.) 10 C.) 15 D.) 18

This is a simple alternating addition and subtraction series.

In the first pattern, 3 is added;

In the second pattern, 2 is subtracted.

Rule =(1st number) (1st number + 3 = 2nd number) (2nd number - 2 = 3rd number) (3rd number + 3 = 4th number)

Now (7) (7 + 3 = 10) (10 - 2 = 8) (8 + 3 = 11) (11 - 2 = 9) (9 + 3 = 12) (12 - 2 = 10)...

So the answer is b = 10.

Logical Reasoning Topics

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