s= 1/7 + 3/7^2 +7/7^3 + 13/7^4 + ........
s = ?
answer 25/108

• s= 1/7 + 3/7^2 +7/7^3 + 13/7^4 + ........
  s/7 = 1/7^2 + 3/7^3 + 7/7^4 + .....
  ----------------------------------------------------
  => s- s/7 = 1/7 + 2/7^2 + 4/7^3 + 6/7^4 ....
  -----------------------------------------------------
  => 6s/7 = 1/7 + 2/7^2 + 4/7^3 + 6/7^4 + ...
  => 6s/7^2 = 1/7^2 + 2/7^3 + 4/7^4 + ....
  -----------------------------------------------------
  => 6s/7- 6s/49 = 1/7 + 1/7^2 + 2/7^3 + 2/7^4 + ....
  => 36s/49 = 1/7 + 1/49 + 2(1/7^3 + 1/7^4 + 1/7^5 +...)
  => 36s/49 = 8/49 + 2* 1/7^3 / (1- 1/7) = 25/49*3
  
  => s = 25/108
  
• 10 years agoHelpfull: Yes(16) No(3)
• @rakesh 25/49*3 is not 25/108 its 25/147
• 10 years agoHelpfull: Yes(3) No(5)
• @hima whr did u gets these questions pls?????????????????
  
• 10 years agoHelpfull: Yes(1) No(0)
• By solving the answer is 25/147
  Can you tell me what's the exact answer is?
  @Hima
• 2 years agoHelpfull: Yes(0) No(0)