7,12,21,38,71,__,__

• the series is 7,(7*2)-2,(12*2)-3,(21*2)-4,(38*2)-5,(71*2)-6 and so on
  so the answer will be 136
• 12 years agoHelpfull: Yes(3) No(1)
• 7=2^2+3
  12=2^3+4
  21=2^4+5
  38=2^5+6
  71=2^6+7
  136=2^7+8
  265=2^8+9....so on
• 12 years agoHelpfull: Yes(2) No(2)
• 136 is the correct answer
  
• 12 years agoHelpfull: Yes(2) No(1)
• ans is 7,12,21,38,71,136,265
  12-7=5=>7-2=5
  21-12=9 => 12-3=9
  38-21=17 => 21-4=17
  71-38=33 => 38-5=33
  next no is 71+(71-6)=136
  ..136+(136-7)=265
• 12 years agoHelpfull: Yes(1) No(1)
• 7=2^2+3
  12=2^3+4
  21=2^4+5
  38=2^5+6
  71=2^6+7
  136=2^7+8
  265=2^8+9
• 12 years agoHelpfull: Yes(1) No(1)
• the next two no. of series 7,12,21,38,71,..,.. is 136 and 257
  reason:
  the pattern of series is 2^(n+1) +(n+2)
  where n=term of series
  therefore to find 6th and 7th we put n=6,7
  we get 6th term = 136 and 7th term=257
• 12 years agoHelpfull: Yes(0) No(4)