Answer: The bacteria took 1 hour and 40 minutes to fill the initial bottle.
Step-by-step explanation: The bacteria took more time to double from 1 cell to a bottle full of cells. Once the bottle was full, each cell in the full bottle doubled, causing an additional bottle to be filled in 5 minutes. Then the 2 full bottles doubled in the next 5 minutes, causing all 3 bottles to be full.
The growth rate is exponential, it doubles every time interval. So by the time you have one bottle, after the next interval you have 2, 4 and so forth.