Insert the missing number
3, 7, 6, 5, 9, 3, 12, 1, 15, ...
A. 18 B. 13
C. -1 D. 3

• Answer is C. -1
  
  Explanation:
  3, 7, 6, 5, 9, 3, 12, 1, 15, ... has two different series
  1) 3, 6, 9, 12, 15.....
  2) 7, 5, 3, 1, ..... -1 is the next number
  
• 13 years agoHelpfull: Yes(20) No(2)
• ans: c i.e. -1
  
  3, 7, 6, 5, 9, 3, 12, 1, 15, ...-1
  4 -1 1 4 -6 9 -11 14 -16
  
• 12 years agoHelpfull: Yes(3) No(5)
• there are two series
  3,6,9,12,15
  7,5,3,1..-1...
• 9 years agoHelpfull: Yes(1) No(0)