I start with a single bacterium. Every minute, every bacterium in the colony splits into two. It takes 60 minutes to completely fill a petri dish. How long did it take for the dish to be exactly half full?
59 minutes
Since the population doubles every minute, the dish would be half full one minute before it is completely full, which is at minute 59.
About this riddle
Math riddles hide a calculation inside a short story. Pull out the numbers, work out what is being asked, and watch for a trick such as a unit change.
Difficulty: Easy. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
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I start with a single bacterium. Every minute, each bacterium splits into two. If the jar is completely full in 60 minutes, at what minute was the jar exactly half full?