Find the missing number in the series.
1. 5760, 960, ? , 48, 16, 8
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, ?
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, ?
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, ?
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.
5. 18, 24, 21, 27, ? , 30, 27
Answer (c). The numbers follow a "+ 6 and - 3" pattern. Thus 18 (+ 6) = 24 (- 3) = 21 (+ 6) = 27 (- 3) = 24 (+ 6) = 30 (- 3) = 27.
6. 2, 5, 10, 17, 26, ?
Answer (b). The numbers are 12 + 1, 22 + 1, 32 + 1, 42 + 1 and so on.
7. 2, 4, 7, 11, 16, 22, ?
Answer (d). The numbers progressively increase by 2, 3, 4, 5, 6 and so on.
8. 4, 2, 5, 3, 6, 4, 7, 5, 8, ?
Answer (c). The numbers follow a "- 2 and + 3" pattern. Thus 4 (- 2) = 2 (+ 3) = 5 (- 2) = 3 (+ 3) = 6 (- 2) = 4 (+ 3) = 7 (- 2) = 5 (+ 3) = 8 (- 2) = 6.
9. 2, 5, 10, 17, 26, 37, ?
Answer (b). The numbers progressively increase by 3, 5, 7, 9, 11, 13 and so on.
10. 7, 14, 23, 34, 47, 62, ?
Answer (a). The numbers progressively increase by 7, 9, 11, 13, 15, 17 and so on. Thus 7 + 7 = 14 + 9 = 23 + 11 = 34 + 13 = 47 + 15 = 62 + 17 = 79.
11. 2, 4, 12, 48, 240, ?
Answer (c). The numbers are progressively multiplied by 2, 3, 4, 5 and 6. Thus 2 x 2 = 4 x 3 = 12 x 4 = 48 x 5 = 240 x 6 = 1440.
12. 1, 5, 4, 10, 9, 15, 16, 20, ?
Answer (b). There are 2 series here. One is 1, 4, 9, 16, 25. The second is 5, 10, 15, 20.
13. 101, 120, 145, 168, 197, ?
Answer (a). The series is 102 + 1 = 101, 112 - 1 = 120, 122 + 1 = 145, 132 - 1 = 168, 142 + 1 = 197, 152 - 1 = 224.
14. 20, 17, 19, 16, 18, 15, ?
Answer (b). The series is 20 - 3 = 17 + 2 = 19 - 3 = 16 + 2 = 18 - 3 = 15 + 2 = 17.
15. 2, 10, 30, 68, 130, ?
Answer (d). The series is 13 + 1 = 2, 23 + 2 = 10, 33 + 3 = 30, 43 + 4 = 68, 53 + 5 = 130, 63 + 6 = 222.