What should come in place of the question mark (?) in the following number series?
15, 12, 17, 10, ?, 8, 21, 6
1
3
2
7
3
21
4
19
5
None of these
What should come in place of the question mark (?) in the following number series?
15, 12, 17, 10, ?, 8, 21, 6