Quote:
Originally Posted by psyang
I think the edge case is taken care of by the fact that a coin doesn't have to be fully on a table. As long as the centre of a coin is on the table (even if it overhangs the edge) it is considered on the table.
The question could be more precisely stated that 100 coin centres are on the table.
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That still doesn't address what I'm getting at. Say you have a coin whose center is more than 2r away from the corner (no other coin is closer to the corner). That means, according to your solution, that another coin can be added to the table, since its center won't fall in the 2r zone. However, this contradicts what the problem says: "it is impossible to add another quarter to the table without requiring an overlap".
So the wording of the problem is causing the confusion here. When it says "impossible to add", does it mean you can't add another coin such that it rests entirely on the table, or does it mean you can't add a coin such that any part of the coin is on the table at all?