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MartyMurray , I dont get it why you are including 3 also from 8  ? The line segment PC has to be less than root over 45 ; not exactly root over 45.  The highlighted part is not clear to me . Can you please help me understand ? MartyMurray KarishmaB
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In rectangle ABCD, if point P (not shown) is to be randomly selected from line segment AB, what is the probability that the length of line segment PC will be less than √45?

Adding point \(P\) and line segment \(PC\) to the the figure, we get the following.



We see that we have a right triangle with sides \(BP\) and \(BC\) and hypotenuse \(PC\).

So, the length of \(PC\) will be \(√45\) when \(BP^2 + 6^2 = (√45)^2\).

In other words, the length of \(PC\) will be \(√45\) when \(BP^2 + 36 = 45\)

So, when \(PC = √45\), \(BP^2 = 9\), and \(BP = 3\).

So, for PC to be less than √45, BP must be less than 3.

Since the length of side \(AB\) is \(8\), \(3/8\) of the points on \(AB\) are less than \(3\) from \(B\).

Thus, the probability that \(PC\) is less than \(√45\) is \(3/8\).

A. 3/8
B. 3/5
C. 4/7
D. 5/8
E. 3/4


The correct answer is (A).
­
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MartyMurray , I dont get it why you are including 3 also from 8  ? The line segment PC has to be less than root over 45 ; not exactly root over 45.  The highlighted part is not clear to me . Can you please help me understand ?
Quote:
Since the length of side \(AB\) is \(8\), \(3/8\) of the points on \(AB\) are less than \(3\) from \(B\).

Thus, the probability that \(PC\) is less than \(√45\) is \(3/8\).

A. 3/8
B. 3/5
C. 4/7
D. 5/8
E. 3/4


The correct answer is (A).
­
­Because, "less than \(√45\)" can be \(√45\) - an infinitely small number, in other words, just ever so slightly less than \(√45\). So, the length of BP can be anything up to just under 3. Thus, effectively, BP can be up to 3/8 of BA since we can ignore the infinitely small difference between the maximum length of BP and 3.­

In other words, the lenght of PC = \(√45\) at a point. A point is infinitely small. So, the length of the line segment BP that does not include that point can effectively be up to 3.
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There will be 3 possible integer points - 0,1,2 (not 3) because when we include 3, PC^2=45 which we don't want. we can take 0 as the length of BP as P can COINCIDE WITH B as well because B is also a point on the line segment AB.
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The length of BP should be less than half of AB, only answer choice is [A] 3/8
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Bunuel, can we expect such question in the focus? It is tagged as prep focus, but isn't geometry not a part of the focus edition?
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Bunuel, can we expect such question in the focus? It is tagged as prep focus, but isn't geometry not a part of the focus edition?

While specific geometry knowledge is not tested on GMAT Focus, not everything involving shapes, volumes, or areas requires specialized geometry knowledge. The area of a square or rectangle, the volume of a cube or rectangular solid, and the Pythagorean theorem are not considered specific geometry knowledge by the GMAT and can still be tested. Moreover, a question can involve shapes but test another area, such as combinations or other topics. There are several questions involving these concepts in the GMAT Prep Focus mocks.­

Some aspects of coordinate geometry are also tested on GMAT Focus under the Functions tag.
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