On a chessboard one white square is chosen at random . In how manyways , can a black square be chosen so that it doesnot lie in the same row as white square.

Any time you are only choosing one of something, the number of ways available to do it is just however many of them you have. Like the number of ways to pick an ace is four, cause there's four of them. It's not the same as picking like two aces, cause then you get into 1) Ace of spades & ace of hearts, 2) ace of spades & ace of diamonds, etc. You're only picking one and there's four choices.

Technically, it's a combination of 1 out of 4, but if you work it out, it's 4.

So how many black squares are there that aren't in the same row as the white square you chose?

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Originally Posted by deepthi03

On a chessboard one white square is chosen at random . In how many ways can a black square be chosen so that it does not lie in the same row as white square.

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Hint: There are 64 squares on a chessboard. Half of them are white. There are eight squares in each row, and half of them are white.

2002