Find the wrong number in the following series.
15, 46, 63, 71, 75, 77, 78,.....

• Ans : 46
  
  Just start from last
  78 - 77 = 1
  77 - 75 = 2
  75 - 71 = 4
  71 - 63 = 8
  note here each difference is double of previous difference
  so the next diff should be "16"
  63 - 16 = 47
  
  but here 46 is there... so wrong no. is " 46"
• 10 years agoHelpfull: Yes(14) No(0)
• Ans: 46
  From 77 and 78 difference=1
  From 75 and 77 difference=2
  From 71 and 75 difference=4
  From 63 and 71 difference=8
  From 47 and 63 difference =16
  From 15 and 47 difference=32
  so, the wrong number is 46
• 10 years agoHelpfull: Yes(0) No(0)