Explanation

 (10 + 20) ÷ 2 = 15

Explanation

 Pattern is ×2 + 1 → (4×2+1 = 9),

(9×2+1 = 19),

(19×2+1 = 39),

(39×2+1 = 79)

Explanation

These are all perfect squares:

- 121 = 11²  

- 144 = 12²  

- 169 = 13²  

- 196 = 14²  

Next number should be:

- 15² = 225

Explanation

Given: 1, 2, 4, 7, 11, ?

The pattern appears to be formed by adding 1, 2, 3, 4, ... to the previous term:

1 + 1 = 2

2 + 2 = 4

4 + 3 = 7

7 + 4 = 11

11 + 5 = 16

Explanation

The pattern is:

-1, -2, -3, -4, …

So the next subtraction is -5.

60 → 59 → 57 → 54 → 50 → 45

Explanation

- First term: 9P0145 → removing 'P' gives 90145  

- Second term: 90159 → 90145 + 14 = 90159  

- Next: 90159 + 14 = 90173

Explanation

The relationship between 4 and 20 is that 20 is 5 times 4.

Similarly, to find the number that corresponds to 5 in the same way, multiply 5 by 6:

4×5=20

5×6=30

Thus, 5 is to 30 in the same way that 4 is to 20.

Explanation

We are given a letter pair sequence: AD, DF, EH, ?

First letters:

- A → D (+3)

- D → E (+1)

- E → G (+2)

So the pattern in first letters is: +3, +1, +2

Second letters:

- D → F (+2)

- F → H (+2)

- H → J (+2)

So the pattern in the second letters is consistently +2

Therefore, the missing pair is:

GJ

Explanation

Each group  is made of 3 consecutive letters in reverse alphabetical order:

- HGF → H, G, F  

- WVU → W, V, U  

- EDC → E, D, C  

Following this reverse-letter pattern:

- After EDC, the next reverse set would be:  

  C, B, A → CAB

Explanation

EFG, LMN, ___, STU

Each group has 3 consecutive letters.

EFG → E, F, G (5th, 6th, 7th letters)  

LMN → L, M, N (12th, 13th, 14th letters)  

STU → S, T, U (19th, 20th, 21st letters)

The missing group must be the letters between N (14th) and S (19th), which are O, P, Q, R.

We need a group of three consecutive letters before S, T, U, after L, M, N.

So after LMN (12,13,14), the next triple is:  

O, P, Q (15,16,17)