9,4,16,6,36,21,441,?

• 421
  
  9 - 4 = 5
  16 - 6 = 10
  36 - 21 = 15
  => 441 - x = 20
  => x = 421
• 12 years agoHelpfull: Yes(43) No(2)
• 421
  
  9,4,16,6,36,21,441,?
  
  if this series is divided into series of pairs we can get
  9,(4,16),(6,36),(21,441)
  4*4=16
  6*6=36
  21*21=441
  so in pair every second no is square of the first no
  now in series every first no of a pais is determined by reducing a multiple of 5 from the second no of previous series such as
  9-(5*1)=4
  16-(5*2)=6
  36-(5*3)=21
  441-(5*4)=421
  
• 12 years agoHelpfull: Yes(2) No(0)
• ans is 421 9-4=5,16-10=6,36-15=21,441-20=421
• 12 years agoHelpfull: Yes(1) No(0)
• ans:421
  
  441-20=421
• 12 years agoHelpfull: Yes(1) No(1)
• 9 , (4 * 4 = 16)
  (6 * 6 = 36 )
  (21 * 21 = 441 )
  (441 * 441 = 19801
• 12 years agoHelpfull: Yes(0) No(9)
• 9-5=4 & 4*4=16
  16-10=6 & 6*6=36
  36-15=21 & 21*21=441
  441-20=421 & 421*421=177241
• 12 years agoHelpfull: Yes(0) No(7)
• answer is 80
  
  3(invisible),3^2,4,4^2,6,6^2,21,21^2
  so there are two serieses-
  3,4,6,21 & 3^2,4^2,6^2,21^2
  
  now 3*1+1=4
  4*2-2=6
  6*3+3=21
  same way 21*4-4=80
• 12 years agoHelpfull: Yes(0) No(3)