← | 029 - Our Dream House | 030 - Cookie Conundrum | 031 - False Memory | → |
Puzzle
- US Version
There are 15 cookies to share amongst a large group. The first person eats one cookie then passes two equal portions of the leftover cookies to two other people. They both eat a cookie then each pass two equal portions of their remaining cookies to two other people, and so on until all of the cookies are gone.
It takes one minute to eat a cookie. Ignoring the time that it takes to pass them, what's the shortest amount of time it could take for all of the cookies to be eaten?
- UK Version
You have 15 biscuits to share among a large group. The first person eats one biscuit and then passes two equal shares of the remaining biscuits to two other people. They both eat a biscuit, and both pass two equal shares of their remaining biscuits to two other people, and so on until all the biscuits are gone.
It takes one minute to eat a biscuit. Ignoring the time it takes to pass them, what's the shortest amount of time, in minutes, that it would take for all the biscuits to be eaten?
Hints
Click a Tab to reveal the Hint.
Solution
Incorrect
Too bad!
- US Version
Clear your mind, and think about it again.
- UK Version
Clear your mind and think about it again.
Correct
- US Version
Correct!
The cookies will be gone in four minutes.
The diagram above shows how you can visualize the puzzle to help you solve it. This seems like the kind of thing that might be useful in real life, but it's not a situation that arises very often, is it?
- UK Version
Crumbs!
The biscuits will be gone in four minutes.
The diagram above shows how you can visualise the puzzle to help you solve it. This seems like the kind of thing that might be useful in real life, but it's not a situation that arises very often, is it?
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