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Re: The three squares above share vertex A with AF = FE and AE = [#permalink]
Say each side of the largest square is 4. This gives a totall area of 16.
Since AF=FE and AE=ED, AF and FE must both equal 1 and ED must equal two. Based on this, the area of the 2nd smallest square is 4 and the smallest square is one...giving us an area of 3 for the shaded region.

Therefore the probability of x being in the shaded region is 3/16. D.
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Re: The three squares above share vertex A with AF = FE and AE = [#permalink]
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the probability of the point to lie in shaded region is giveny by

area of the shaded region / area of the original square

To find the area of shaded region = area of the square formed by side AE - area of the square formed by side AF

If we assume that the side AD = 1 unit; then from given info we can take AF = 1/4 and AE = 1/2

Then the area of the square formed by side AE would be 1/4 and the area of the square formed by side AF would be 1/16
Therefore, area of the shaded region = 1/4 minus 1/16 = 3/16

We can take this 3/16 directly as probability because the area of the original square is 1 unit from out assumption of orginal side to be 1 unit.

thanks
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Re: The three squares above share vertex A with AF = FE and AE = [#permalink]
MacFauz wrote:
fozzzy wrote:
The three squares above share vertex A with AF = FE and AE = ED. If a point X is randomly selceted from square region ABCD, what is the probability that X will be contained in the shaded region?

A) 1/16
B) 1/12
c) 1/4
D) 3/16
4) 1/3


Lets say AD = 4, So, AE = 2 & AF = 1.

Area of ABCD = 16
Area of Square with side AE = 4
Area of Square with side AF = 1

Area of shaded region = 4-1 = 3

Probability = \(\frac{Area of shaded region}{Area of ABCD}\) = \(\frac{3}{16}\)

Answer is D.


how do we know AE = 2 and AF = 1 instead of the reverse order?
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Re: The three squares above share vertex A with AF = FE and AE = [#permalink]
sagnik242 wrote:
MacFauz wrote:
fozzzy wrote:
The three squares above share vertex A with AF = FE and AE = ED. If a point X is randomly selceted from square region ABCD, what is the probability that X will be contained in the shaded region?

A) 1/16
B) 1/12
c) 1/4
D) 3/16
4) 1/3


Lets say AD = 4, So, AE = 2 & AF = 1.

Area of ABCD = 16
Area of Square with side AE = 4
Area of Square with side AF = 1

Area of shaded region = 4-1 = 3

Probability = \(\frac{Area of shaded region}{Area of ABCD}\) = \(\frac{3}{16}\)

Answer is D.


how do we know AE = 2 and AF = 1 instead of the reverse order?


Hi,
A per Q, AF = FE. So, AE = 2*AF.
If we assume AF = 1, it implies AE = 2.
Hope that helps.
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Re: The three squares above share vertex A with AF = FE and AE = [#permalink]
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fozzzy wrote:
Attachment:
Untitled.png
The three squares above share vertex A with AF = FE and AE = ED. If a point X is randomly selceted from square region ABCD, what is the probability that X will be contained in the shaded region?

A. 1/16
B. 1/12
C. 1/4
D. 3/16
E. 1/3


Let AF=FE=1, with the result that AE=ED=2:

As the figure illustrates:
shaded region = 1+1+1 = 3
ABCD = 4*4 = 16
\(\frac{shaded}{ABCD} = \frac{3}{16}\)

.
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Re: The three squares above share vertex A with AF = FE and AE = [#permalink]
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Re: The three squares above share vertex A with AF = FE and AE = [#permalink]
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