A secret can be told to only 2 persons in 3 minutes. Each person in turn tells 2 other persons in the next 3 minutes and the processes continues accordingly. In 30 minutes how many persons can be told this secret in this way?

a) 1024 b) 2048 c) 512 d) 4096

• 2^1 + 2^2 + 2^3 + 2^4 + ..............+2^10 =>2048(b)Ans.
• 11 years agoHelpfull: Yes(2) No(0)
• in 3 min 1 person say the secret to 2 people.
  in 6 min (1+2=3) peroson say the secret to 6 people
  in 9 min (3=6=9)person say the secret to 18 people.
  see each n every time the no is multiplied by 3.(ie2 then 6 then 18)
  so total no of person knw the secret in nxt 31 min=18*3^7=39366
  
  so similarly
• 11 years agoHelpfull: Yes(0) No(1)
• 2^10=1024
  remaining is same as manish sir solution
  
• 10 years agoHelpfull: Yes(0) No(0)
• IN 3 MIN 2
  IN 6 MIN 4
  .
  .
  .IN 30 MIN 1024 (ANS)
• 7 years agoHelpfull: Yes(0) No(0)
• 2^1 + 2^2 + 2^3 + 2^4 + ..............+2^10 = 2(2^10 - 1)/(2-1)
  = 2*1023 = 2046
• 7 years agoHelpfull: Yes(0) No(0)