**21) 9, 27, 31, 155, 161, 1127, ?**

**Answer**: 1135

**Explanation**: x 3, + 4, x 5, + 6, x 7,….. So, 1127 + 8 = 1135

**22) 2, 1, 2, 4, 4, 5, 6, 7, 8, 8, 10, 11, ?**

**Answer**: 10

**Explanation**: I. 1st, 4th, 7th, 10th, 13th, II. 2nd, 5th, 8th, 11th, III. 3rd, 6th, 9th, 12th So, the missing term is 10

**23) 13, 32, 24, 43, 35, ?, 46, 65, 57, 76**

**Answer**: 54

**Explanation**: I. 13, 24, 35, 46, 57 and II. 32, 43, ?, 65, 76 So, 43 + 11 = 54

**24) 22, 24, 28, ?, 52, 84**

**Answer**: 36

**Explanation**: + 2, + 4, + 8, + 16,….. So, 28 + 8 = 36

**25) 3, 15, ?, 63, 99, 143**

**Answer**: 35

**Explanation**: (22 – 1), (42 – 1),….., (82 – 1), (102 – 1), (122 – 1) So, (62 – 1) – (36 – 1) = 35

**26) 90, 180, 12, 50, 100, 200, ?, 3, 50, 4, 25, 2, 6, 30, 3**

**Answer**: 150

**Explanation**: 90 = 30 x 3, 180 = 6 x 30, 12 = 2 x 6, 50 = 25 x 2, 100 = 4 x 25, 200 = 50 x 4. So, 3 x 50 = 150

**27) 48, 24, 96, 48, 192, ?**

**Answer**: 96

**Explanation**: Ã· 2, x 4, Ã· 2, x 4, ….. So, 192 Ã· 2 = 96

**28) 2,15,41,80,?**

**Answer**: 132

**Explanation**: + 13, + 26, + 39,….. So, 80 + 52 = 132

**29) 6, 11, 21, 36, 56, ?**

**Answer**: 81

**Explanation**: + 5, + 10, + 15, + 20, … So, 56 + 25 = 81

**30) 563, 647, 479, 815, ?**

**Answer**: 143

**Explanation**: + 84, – 168, + 336,…..i.e. + 84, – (84 x 2), + (84 x 22), ….. So, 815 – (84 x 23) = 815 – 672 = 143