Q.1-find the wrong number in the following series

(a) 1,2,4,11,15,22,29,............

(b) 2,10,30,68,130,220,...........

(c) 1,3,7,15,31,57,...............

• x^3+x
  if x=1---->1^3+1=2
  x=2---->2^3+2=10
  :
  :
  x=6---->6^3+6=222
  ans is:b
• 10 years agoHelpfull: Yes(1) No(0)
• b): here 2,10,30,68,130,220 are in the series of 1^3+1 2^3+2,3^3+3,4^3+4,5^3+5,6^3+6 so 220 is the wrong no.of this series.
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• c):it is the series of 1*2+1,3*2+1,7*2+1,15*2+1and31*2+1 so its ans.is 57
  
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• I could not crack the first one, sorry about that.
  
  For the second one
  2 is 1 cube + 1; 10 is 2 cube + 2; 30 is 3 cube + 3; 68 is 4 cube + 4; 130 is 5 cube + 5; the next number should be 6 cube + 6, and it should be 222
  
  So, 220 is the wrong number
  
  For the one,
  1 * 2 + 1 =3, 3* 2 + 1 = 7; 7* 2 + 1 = 15, 15 * 2 + 1 = 31, 31 * 2 + 1 = 63
  
  So, 57 is the wrong answer
  
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