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Intern
Joined: 04 Jan 2012
Posts: 4

Kudos [?]: 17 [0], given: 3

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27 Mar 2012, 18:34
Hi, I need some clarity on quadrilaterals concepts/rules. Meanwhile I also have a DS question for which I am looking for an explanation. Please help. Thank you.

1) 3 sides are equal
2) 3 angles are 90 degrees.

Kudos [?]: 17 [0], given: 3

Magoosh GMAT Instructor
Affiliations: Magoosh
Joined: 28 Nov 2011
Posts: 31

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Location: United States (CA)

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27 Mar 2012, 18:46
Here's a lesson video that gives an overview of quadrilaterals.

As for the question, Statement A alone could be true of a trapezoid, and Statement B could just as well be a rectangle, so you need both statements ("Both statements 1 and 2 together are sufficient to answer the question but neither statement is sufficient alone"), which means the answer is C.

I hope that helps, feel free to let me know if you have any other questions!
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Margarette
Magoosh Test Prep

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Senior Manager
Status: May The Force Be With Me (D-DAY 15 May 2012)
Joined: 06 Jan 2012
Posts: 272

Kudos [?]: 320 [0], given: 16

Location: India
Concentration: General Management, Entrepreneurship

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27 Mar 2012, 20:37
Ya its +1c

Posted from my mobile device
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Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 7672

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28 Mar 2012, 01:58
saishankari wrote:

1) 3 sides are equal
2) 3 angles are 90 degrees.

Think of it this way:
Stmnt 1. Even if all 4 sides are equal, it still may not be a square. It may be a rhombus (angles are not 90 degrees). Clearly not sufficient.
Stmnt 2. 3 angles 90 degrees means the fourth angle has to be 90 degrees too (since the sum of all interior angles of a quadrilateral is 360 degrees). But if a quadrilateral has all four angles 90, does it mean it is a square? No. It could be a rectangle. Only opposite sides are equal in length in a rectangle. Not sufficient.

Using both statements: The quadrilateral must have all four angles 90 degrees. Since 3 sides are equal, the fourth one must be equal to these 3 since the pair of opposite sides must be equal if all four angles are 90 degrees. Hence, the quadrilateral must be a square.

As for:
Hi, I need some clarity on quadrilaterals concepts/rules.

I would suggest you to check out the Veritas Geometry book. It covers lines, angles, triangles, quadrilaterals, circles, 3 D figures, co-ordinate ... pretty much everything you might see on GMAT.
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Karishma
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