Princeton Review Drill - I don't understand : GMAT Problem Solving (PS)
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# Princeton Review Drill - I don't understand

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Intern
Joined: 24 Aug 2011
Posts: 7
Location: United States (AL)
GMAT Date: 08-03-2012
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Kudos [?]: 5 [0], given: 3

Princeton Review Drill - I don't understand [#permalink]

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30 Aug 2011, 04:06
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Question Stats:

14% (01:06) correct 86% (00:24) wrong based on 7 sessions

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In the PR Cracking the GMAT 2012 (Drill 7 #8 pg 196) there is a triangle not drawn to scale. It "appears" to be a an isosceles triangle with the the diagram drawn: Lower left angle is ~60 degrees with leg value A. Angle labeled X. The "top point" of the triangle at the top is labeled B with and drawn ~30degrees. No angle label. The final angle (lower right) is drawn ~60 degrees (labeled Y) and the leg is labeled C. The data sufficiency question is:

What is the value of x in ABC shown above?
1) Angle y = 80 degrees
2) AB = BC

[Reveal] Spoiler:
I quickly determined it could only be C or E but chose the answer C because, if we know AB=AC and they are shown opposite the angles X and Y, can't we determine that X also equals 80 degrees? The PR says the answer is E beause "we don't actually know the two sides of the triangle are equal."

I'm confused - what does AB=BC mean if it doesn't mean they are equal? I appreciate any help you can give me. NC
[Reveal] Spoiler: OA

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Last edited by Nchoward on 30 Aug 2011, 06:20, edited 1 time in total.
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Re: Princeton Review Drill - I don't understand [#permalink]

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30 Aug 2011, 06:13
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Why not c?

If we know that AC=AB, then y and z (the angle at b) are equal and both 80°, hence 160 in total. Therefore, x is 20
Intern
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Re: Princeton Review Drill - I don't understand [#permalink]

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30 Aug 2011, 06:22
Berbatov wrote:
Why not c?

If we know that AC=AB, then y and z (the angle at b) are equal and both 80°, hence 160 in total. Therefore, x is 20

THANKS - but I totally copied the problem incorrectly! The sides that = each other are AB and BC.

Sorry for the confusion. NC
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Re: Princeton Review Drill - I don't understand [#permalink]

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30 Aug 2011, 06:24
Nchoward wrote:
Berbatov wrote:
Why not c?

If we know that AC=AB, then y and z (the angle at b) are equal and both 80°, hence 160 in total. Therefore, x is 20

THANKS - but I totally copied the problem incorrectly! The sides that = each other are AB and BC.

Sorry for the confusion. NC

Should still be c though^^

If both legs are equal, y and x also have to be equal...
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Re: Princeton Review Drill - I don't understand [#permalink]

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10 Nov 2011, 20:20
It definitely looks like it should be C. I am in the same boat. Just starting my review and I'd hate to get something seemingly basic like this incorrect...is this confirmed?
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Re: Princeton Review Drill - I don't understand [#permalink]

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22 Nov 2011, 06:38
No values given.
we need to find x.
1.y=80 deg. We cannot find x from this since we don't know the other angle. NOT SUFFICIENT
2.given: AB=BC. implies x = y. But y = unknown. NOT SUFFICIENT
If both are taken together, y=80 AND x=y, hence x=80. Hence, C.
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Re: Princeton Review Drill - I don't understand [#permalink]

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23 Nov 2011, 06:40
Unless you made some error copying the question, the OA is incorrect. It should be C. If AB=BC, implies, it is an isosceles triangle. Hence, X=Y, and Y is given as 80. Thus X=80.

I don't see how E can be the answer.
Re: Princeton Review Drill - I don't understand   [#permalink] 23 Nov 2011, 06:40
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