18
12
15
The answer is: 12.
44
44
The next number in the series 10, -5, 25, -35, 85, -155 is:
21 - each number in the series increases by the series 1,2,3,4,5.... Whereby 6 and 7 are separated by 1, 7 and 9 are separated by 2, 9 and 12 are separated by 3, 12 and 16 are separated by 4, so the next in the series would be 21 (16 and 21 are separated by 5).
The next number in the series 1 2 4 8 10 20 22 is
These are squares. 12 = 1 22 = 4 32 = 9 (it is missing 42 = 16) 52 = 25 62 = 36 The next one in the series is probably 72 = 49.
550
25-1=24 24-2=22 22-3=19 19-4=15 15-5=10 The next number in the series is 10.