Two white squares and a black square have to be chosen from a chess board such that no two of them are in the same row or column. In how many ways can the selection be made?
a) 6912
b) 6712
c) 6942
pls explain.....

The number of ways in which the first white square can be selected = 32
Now, number of ways in which a black square can be selected = 24 (Not in the same row or column as the white square)
Next, number of ways of selecting the other white square = 32 - (4+3+4+3) = 18
The selection of the two white squares should be divided by 2 to account for repetition.

Total number of ways of selection = 32*24*18/2 = 16*24*18 = 6912