```
```1) 13, 9, 12, 17, 21

A. 21

B. 17

C. 12

D. 3

**Answer:**C. 12

**Explanation:**
Each of the numbers except 12 is an odd number.

The number '12' is the only EVEN number.

So the answer is 12.

```
```2) 1, 8, 27, 64, 100, 125, 216

A. 27

B. 100

C. 125

D. 216

**Answer:**B. 100

**Explanation:**
The pattern is 13 23, 33, 43, 53, 63. But, 100 is not a perfect cube.

```
```3) 10, 15, 25, 58, 45, 55, 60

A. 10

B. 45

C. 58

D. 60

**Answer:**C. 58

**Explanation:**
Each of the numbers except 58 is multiple of 5.

```
```4) 3,6, 9, 12, 21, 24, 26, 30

A. 26

B. 21

C. 24

D. 30

**Answer:**A. 26

**Explanation:**
Each of the numbers except 26, is a multiple of 3.

```
```5) 1, 2, 6, 15, 31, 56, 91

A. 23

B. 92

C. 100

D. 112

**Answer:**B. 92

**Explanation:**
1, 1 + 12 = 2, 2 + 22 = 6, 6 + 32 = 15,

15 + 42 = 31, 31 + 52 = 56, 56 + 62 = 92

Last number of given series must be 92 not 91.