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Can someone explain this tile question?

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Manager
Joined: 02 Apr 2010
Posts: 99
Followers: 1

Kudos [?]: 3 [0], given: 1

Can someone explain this tile question? [#permalink]  26 Dec 2010, 23:01
00:00

Difficulty:

45% (medium)

Question Stats:

58% (02:17) correct 41% (01:18) wrong based on 31 sessions
100 white and black tiles will be used to form a 10x10 square pattern. If there must be at least one black tile in every row and at least one white tile in every column, what is the maximum difference between the number of black and white tiles that can be used?

75
80
85
90
95
[Reveal] Spoiler: OA
Manager
Joined: 17 Sep 2010
Posts: 216
Concentration: General Management, Finance
GPA: 3.59
WE: Corporate Finance (Entertainment and Sports)
Followers: 3

Kudos [?]: 13 [0], given: 33

Re: Can someone explain this tile question? [#permalink]  26 Dec 2010, 23:14
ohfred wrote:
100 white and black tiles will be used to form a 10x10 square pattern. If there must be at least one black tile in every row and at least one white tile in every column, what is the maximum difference between the number of black and white tiles that can be used?

75
80
85
90
95

80?

90 white or black subtracted from 10 white or black.

At first I got 90, but realized the double counting I was doing.
Manager
Joined: 31 May 2010
Posts: 97
Followers: 1

Kudos [?]: 18 [1] , given: 23

Re: Can someone explain this tile question? [#permalink]  26 Dec 2010, 23:53
1
KUDOS
You required 100 tiles in total
As per question we have to find maximum difference possible between white and black tiles.
So, we have to find, as per condition, maximum white tiles(black) can be used and minimum blac tiles(white) tiles that must be used.

In any case, maxium black and white tiles that can be used to form the square is 90.( 9 tiles of same color in any row or column:: 9 * 10).
and minimum blac or white tiles that can be used to form the squaare is 10( 1 tiles every row or column = 1 * 10 )

90 - 10 = 80
_________________

Kudos if any of my post helps you !!!

Re: Can someone explain this tile question?   [#permalink] 26 Dec 2010, 23:53
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