Each cell of a certain kind of bacteria produces two more cells. The life span of each cell is 10 minutes and each cell multiples only once in its life time, when it is exactly one minute old. If a new cell is placed in an empty box at time t = 0, then how many live cells will be there in the box just after t = 20 minutes?
(1) 2048 × 1023 (2) 1024 × 1023 (3) (1024)² (4) 1023 × 1025

• see total cells created after
  1min be 2^1
  2min be 2^2
  3 min be 2^3.......
  thus after 20 min 2^20 will be created
  now after 10 min 1 cell will die (2^0)
  after 11 min 2 cells die (2^1)
  similarly after 20 min 2^10 cells die
  thus total cells remained=(2^20)-(1024)
  or (1024)^2-1024
  or1024*(1024-1)
  i.e, 1024*1023
• 10 years agoHelpfull: Yes(23) No(0)
• since a cell is kept at t=0
  then at t=9 cells=2^10=1024
  at t=10 ,1 cell dies then remaining cells=1023
  at t=19 , cells =2^10=1024
  but 1 cell dies then remaining cells=1023
  at t=20 1 new cell borns then total cells=1023+1=1024
  so the correct answer is 1024 x 1023
• 10 years agoHelpfull: Yes(10) No(4)
• 2^11 + 2^12 +......+ 2^20 = 1023 X 2048....
• 10 years agoHelpfull: Yes(8) No(4)
• Can you please explain more precisely
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