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

B0R , E3U , G9Y , J18D , ?

A. E30P

B. H27N

C. L30J

D. G33U

**>** To get the first letter of a term, add 3 and 2 alternately to the position of the first letter of the previous term.

**B** (C D) **E** (F) **G** (H I) **J** (K) **L**

**> **The numbers form a series in which the successive multiple of 3 is added to obtain the next term.

0 + 3 = 3

3 + 6 = 9

9 + 9 = 18

Therefore, the number in the next term = 18 + 12 = 30

**>** The last letters of each term – R, U, Y, D form a series with gaps of 2, 3 and 4 letters. Therefore, the last letter of the next term is J.

**R** (S T) **U** (V W X) **Y** (Z A B C) **D** (E F G H I) **J**

Therefore, the next term is L30J. **So, C is the correct option.**

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

A729, G343, ?, S27, Y1

A. L64

B. M75

C. Q100

D. M125

**>** To get the next letter of a term, add 6 to the position of the letter of the previous term. Following this pattern, the letter of the missing term would be M.

**A** (BCDEF) **G** (HIJKL) **M** (NOPQR) **S** (TUVWX) **Y** Z

**> **The number form a series of cubes of decreasing consecutive odd numbers.

9^{3} = 729

7^{3} = 343

**5 ^{3} = 125**

3^{3} = 27

1^{3} = 1

Therefore, the number in the missing term is 125.

Hence, the missing term is M125. **So, D is the correct option.**

**Practice Exercise 3: What should come in place of question mark (?) in the following letter series?**

Q331T, U442X, Y553B, ?

A. Z665D

B. C664F

C. B666D

D. B664F

**>** To get the first letter of a term, add 1 to the position of the last letter of the previous term. Hence, the first letter of the next term would be C.

**> **The numbers form a series with a common difference of 111. Therefore, the number in the next term = 553 + 111 = 664

**>** To get the last letter of a term, add 3 to the position of the first letter of the same term. Hence, the last letter of the next term would be F.

Therefore, the next term is C664F. **So, B is the correct option.**

**Practice Exercise 4: What should come in place of question mark (?) in the following letter series?**

RL12, TQ20, WU32, AX48, ?

A. EZ68

B. FZ68

C. GZ68

D. HZ68

**>** The first letters of each term – R, T, W, A form a series with gaps of 1, 2 and 3 letters. Therefore, the first letter of the next term is F.

**R** (S) **T** (UV) **W** (XYZ) **A** (BCDE) **F**

**> **The second letters of each term – L, Q, U, X form a series with gaps of 4, 3 and 2 letters. Therefore, the second letter of the next term is Z.

**L** (MNOP) **Q** (RST) **U** (VW) **X** (Y) **Z**

**>** The numbers – 12, 20, 32, 48 form a series in which the difference between the consecutive terms increases by 4 every next term.

12 + 8 = 20

20 + 12 = 32

32 + 16 = 48

48 + 20 = 68

Therefore, the number in the next term is 68.

Hence, the next term is FZ68. **So, B is the correct option.**

**Practice Exercise 5: What should come in place of question mark (?) in the following letter series?**

VR, YT, BV, EX, ?

A. FZ

B. GZ

C. HB

D. HZ

**>** To get the first letter of a term, add 3 to the position of the first letter of the previous term. Hence, the first letter of the next term would be H.

**V** (WX) **Y** (ZA) **B** (CD) **E** (FG) **H**

**>** To get the second letter of a term, add 2 to the position of the second letter of the previous term. Hence, the first letter of the next term would be Z.

Therefore, the next term would be HZ. **So, D is the correct option.**