Q20 Talent Test

0 votes

Consider an 8X8 chess board. The number of ways 8 rooks can be placed in the board so that no 2 rooks are in a same row or column?

(A) 40,320

(B) 80,640

(C) 5040

(D) 720

asked Apr 8, 2017 in Aptitude by getgatebook (33,570 points)
reshown Apr 9, 2017 by getgatebook

1 Answer

+1 vote

(A)

 

We can solve this by using either rows or columns approach. Lets do by rows. For 1st row we, have 8 options to place the 1st rook. For 1st row, we have 8 choices, for 2nd row 7 choices and so on...so 8! = 40320.

Note that we should not count possibilities by BOTH rows and columns as they give us the same set of 8!

possibilities.

answered Apr 9, 2017 by chandrasish96 (360 points)
Answer:
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