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Find the missing number in the series.

1. 5760, 960, ? , 48, 16, 8

240

192

160

120

Answer (b). First number is divided by 6 to get the second and the second is divided by 5 to get the third and the third is divided by 4 to get the fourth number and so on.

2. 3, 9, 21, 39, ?

72

53

63

51

Answer (c). The numbers progressively increase by multiples of 6. Thus, the difference between 9 and 3 is 6, between 21 and 9 is 12, between 39 and 21 is 18. Hence 39 + 24 = 63

3. 1, 0, 3, 2, 5, 6, ?

9

8

10

7

Answer (d). There are 2 series here. One is 1, 3, 5, 7. The second is 0, 2, 6, 12.

4. 1, 1, 2, 3, 5, 8, 13, ?

17

21

23

19

Answer (b). Starting from 2, each number is the sum of preceding 2 numbers. Thus 1 + 1 = 2 + 1 = 3 + 2 = 5 + 3 = 8 + 5 = 13 + 8 = 21.

Answer (b). The numbers progressively decrease by multiples of 3 starting with 9. Thus 1438 - 1429 = 9, 1429 - 1417 = 12, 1417 - 1402 = 15. 1402 - 17 = 1384.

17. 1, 3, 6, 10, 15, ?

18

21

19

20

Answer (b). The numbers progressively increase by 2, 3, 4, 5, 6 etc.

18. 8, 17, 36, 75, 154, ?

293

313

342

265

Answer (b). (8 x 2) + 1 = 17; (17 x 2) + 2 = 36; (36 x 2) + 3 = 75.

19. 10, 100, 200, 310, ?

400

410

420

430

Answer (d). The difference between successive numbers is 90, 100, 110. Hence the difference between the next number and 310 should be 120. Thus 310 + 120 = 430.

20. 4/12/11, 1/1/12, 29/1/12, 26/2/12, ?

24/3/12

25/3/12

26/3/12

27/3/12

Answer (b). The difference between two consecutive dates is 28 days. Note: 2012 was a leap year.

21. 2, 3, 10, 29, 66, ?

89

99

127

130

Answer (c). The difference between the numbers is 1, 7, 19, 37. The difference between the numbers so obtained is 6, 12, 18. Hence the difference between the next number and 66 should be 37 + 24 = 61. Thus 66 + 61 = 127.

22. 1, 2, 6, 21, ?

88

86

67

62

Answer (a). 1 x 1 + 1 = 2; 2 x 2 + 2 = 6, 6 x 3 + 3 = 21; 21 x 4 + 4 = 88

23. 2460, 3570, 4680, ?

8640

5670

5970

5790

Answer (d). Number formed by first 2 digits increases by 11 in each consecutive number, while the number formed by the last 2 digits increases by 10.

24. 7714, 7916, 8118, ?

8320

8312

8520

8515

Answer (a). The first 2 digits are a sequence of odd numbers starting from 77 and the last 2 digits are a sequence of even numbers starting from 14.