Find the 87th number in the series 2, 10, 26, 50
a) 160
b) 260
c) 60
d) None

• nth term is 2 + (8 + 16 + 24 + ... (n-1) terms )
  => nth term = 2 + [ (n-1)(2*8 + 8n - 16)/2 ]
  = 2 + 4n(n-1)
  = 4n^2 - 4n + 2
  
  => 87th term = 4*87^2 - 4*87 + 2 = 29930
• 11 years agoHelpfull: Yes(1) No(3)
• ans is none.. bcoz ans is 29930
• 11 years agoHelpfull: Yes(0) No(3)
• 2 = 1^2 + 1
  10 = 3^2 +1
  26 = 5^2 + 1
  50 = 7^2 + 1
  Now,
  1,3, 5, 7 ...... forms a AP series with common difference 2.
  So, we will find T87 firs through Ap.
  Tn = a +(n-1)*d
  Tn = 1 + (87 -1) *2 = 1 + 86 *2 = 173.
  Now,
  87th term = 1732 + 1 = 29929 + 1 = 29930.
• 8 years agoHelpfull: Yes(0) No(0)