It could be 62.
12
31
38
20
The series appears to be decreasing by progressively smaller factors. Each number is obtained by dividing the previous number by a decreasing factor: 5000 divided by 5 gives 1000, 1000 divided by 5 gives 200, and 200 divided by 5 gives 40. Continuing this pattern, 40 divided by 5 gives 8, so the next number in the series is 8.
The next number is 20.
31
31.
12
The HCF of 38 and 40 is 2
38
31
38
In a series of numbers, there are rhythms that change. In the order of 100, 140, and 40, the number that would come next would be 80 because 40 should be added.
20
6
8, each number is a fifth of the last.