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Area of a square

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by pareekbharat86 » Tue Nov 19, 2013 1:59 am
Image

In the diagram above, the fourteen rectangular tiles are all identical. What percent of the area of rectangle ABCD is covered by the tiles?

(1) ABCD is a square.

(2) EFGH is a square.
Thanks,
Bharat.
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Source: — Data Sufficiency |

by GMATGuruNY » Tue Nov 19, 2013 5:39 am
pareekbharat86 wrote:Image

In the diagram above, the fourteen rectangular tiles are all identical. What percent of the area of rectangle ABCD is covered by the tiles?

(1) ABCD is a square.

(2) EFGH is a square.
Statement 1: ABCD is a square
For ABCD to be a square, the length of each tile must be twice the width, as the cases below will illustrate.

Case 1: Each rectangle is 2 feet by 1 foot
Image
Area of ABCD = 8*8 = 64.
Area of the 14 tiles = 14*2*1 = 28.
Resulting ratio:
(tile area)/(total area) = 28/64 = 7/16.

Case 2: Each rectangle is 4 feet by 2 feet
Image
Area of ABCD = 16*16 = 256.
Area of the 14 tiles = 14*4*2 = 112.
Resulting ratio:
(tile area)/(total area) = 112/256 = 56/128 = 7/16.

The resulting ratio is THE SAME in each case.
The implication is that -- in EVERY case -- the following ratio will be yielded:
(tile area)/(total area) = 7/16.
SUFFICIENT.

Statement 2: EFGH is a square
For EFGH to be a square, ABCD must also be a square.
Thus, statement 2 implies the same information as statement 1.
Since statement 1 is sufficient, statement 2 also is SUFFICIENT.

The correct answer is D.
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by Mathsbuddy » Tue Nov 19, 2013 9:47 am
X = length of AB = BC = CD = AD
Y = length of EF = FH = HG = EG
L = length of rectangle
W = width of rectangle

X = 3L + 2W = 4L
so area X^2 = 16L^2

Y = 3L
so area Y^2 = 9L^2

(X^2 - Y^2)/X^2 = (16-9)/16 = 7/16 = 43.75%
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by pareekbharat86 » Tue Nov 19, 2013 8:42 pm
OA is indeed D.
Thanks,
Bharat.
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