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Tagged with checkerboard no-computers
2 questions
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5
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How can 3 queens control the white squares?
It is well known that there is no way of arranging 4 queens on a checker board in such a way that every square is occupied or threatened.
Now consider a slight variation where we only need to cover ...
- 10.4k
18
votes
4
answers
2k
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Paint 21 Squares of a 7×7 Board Without Forming a Rectangle
Got a nice puzzle from my friend, when he was competing in IWYMIC/IMC 2011.
Paint $21$ of the $49$ squares of a $7 \times 7$ board so that no four painted squares form the four corners of a rectangle....
- 34.4k