MathDB

6

Part of 2009 Swedish Mathematical Competition

Problems(1)

reverse any 5 coins in a row from a total of 289 coins in a 17x17 grid

Source: 2009 Swedish Mathematical Competition p6

4/27/2021
On a table lie 289289 coins that form a square array 17×1717 \times 17. All coins are facing with the crown up. In one move, it is possible to reverse any five coins lying in a row: vertical, horizontal or diagonal. Is it possible that after a number of such moves, all the coins to be arranged with tails up?
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