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.

93 = 729

73 = 343

53 = 125

33 = 27

13 = 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.