A biochemist is cultivating living cells. Each cell splits into two cells after one minute. One minute later the two cells split to make four, then the four become eight, and so on. Every minute the number of cells doubles.
Assume that it takes an hour for one cell to grow until a bottle is filled. If the chemist starts with two cells, how long will it take to fill the same bottle?
Some may say 30 minutes but if you think about it, the answer is 59 minutes since it only takes one minute for the cells to double in number.
I find that this puzzle is most effective when told in a casual and extempore manner. If you make it sound like just a simple puzzle, it can be rather disarming (depending on your style of delivery, of course) and some people wouldn’t give it much of a thought. I first heard this puzzle from my third-grade teacher, though I wasn’t caught off guard as I tend to listen to puzzles attentively.