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- (From our friend, @jamestanton):The number 21200 is
*self-describing*: it has 2 zeros,1 one, 2 twos, 0 threes, and 0 fours. How many 5-digits numbers almost like this? How many are correct in 4 of the 5 digits? - Can you plant exactly seven trees, so that there are exactly six rows, each containing exactly three trees?
- Is it possible to slice a cube with a straight plane to get a pentagon? Is it possible to slice a cube with a straight plane to get a regular pentagon? Is it possible to slice a cube with a straight plane to get a regular hexagon?
- The number \(2015!\) is a really large number. It is equal to $$1 \times 2 \times 3 \times \cdots \times 2014 \times 2015$$ How many zeros does it end with?

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