Find the missing number in the following series

Q51. 1961, ?, 121, 29, 6

1. 490
2. 489
3. 488
4. 487

Q52. 70, 35, 14, 4.66, ?

1. 1.33
2. 0.084
3. 0.84
4. 8.04

Q53. 2, 10, 45, 231, 1393, ?

1. 9195
2. 7959
3. 9759
4. 9751

Q54. 2807, 1400, 697, 346, 346, 171, 84, 41, ?

1. 22
2. 19
3. 20
4. 21

Q55. 81, 192, 375, ?, 1029

1. 684
2. 486
3. 648
4. 468

Q56. 1, 4, 15, 64, 325, ?

1. 1630
2. 2275
3. 1956
4. 1950

Q57. 81, 41, 42, 64.5, ?, 330

1. 131
2. 118.5
3. 129
4. 105.5

Q58. 15, 30, ?, 40, 8, 48

1. 10
2. 20
3. 30
4. 15

Q59. 10, 11, 18, 38, 97.5, 295.5, ?

1. 796
2. 1186
3. 889.5
4. 1037.75

Q60. 4, 6, ?, 30, 90, 315

1. 9
2. 12
3. 15
4. 8