First coin can be placed in one of 25 places. For second, only 16 places
are possible because of the same column and same row condition.
Similarly, only 9 places for third coin. So, total ways = 25 * 16 * 9.
but since coins are identical you can't distinguish one from another and
thus final answer is ( 25*16*9 ) / 3 = 1200.

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