**Practice Exercise 1: What should come in place of question mark (?) in the following letter series?**

AZ , GT , MN , ? , YB

A. KF

B. RX

C. SH

D. TS

**>** To get the first letter of a term, add 6 to the position number of the first letter of the previous term. Hence, the first letter of the missing term would be S.

**> **The position number of the first letter in the English alphabet is same as the position number of the second letter in the English alphabet in reverse order. Thus, the second letter of the missing term would be H.

Therefore, the missing term is SH. **So, C is the correct option.**

**Practice Exercise 2: What should come in place of question mark (?) in the following letter series?**

J2Z, K4X, I7V, ?, H16R, F22P

A. I11T

B. L11S

C. L12T

D. G11T

**> ** The difference between the numbers in the consecutive terms increases by 1 every next term.

2 + 2 = 4

4 + 3 = 7

**7 + 4 = 11**

11 + 5 = 16

16 + 6 = 22

Therefore, the number in the missing term is 11.

**>** The first letters of the terms form a series in the group of 3.

Consider J, K, I. To get the second letter of the group, add one to the position number of the first letter of the group. To get the third letter of the group, subtract one from the position number of the first letter of the group.

Thus, the first letter of the missing term is G.

**> **To get the last letter of a term, subtract 2 from the position number of the last letter of the previous term. Hence, the last letter of the missing term would be T.

Therefore, the missing term is G11T. **So, D is the correct option.**

**Practice Exercise 3: Complete the following series:**

gfe___ig___eii___fei___gf___ii

A. e i f g i

B. f i g i e

C. i f g i e

D. i f i g e

It is a repetition of the string: gfeii.

The missing letters in the blanks are: i f g i e. **Therefore, C is the correct option.**