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Is ABCD a square ? 1. ABCD is a trapezium. 2. ABCD is not a

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Manager
Joined: 30 Jun 2006
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Is ABCD a square ? 1. ABCD is a trapezium. 2. ABCD is not a [#permalink]

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28 Jul 2006, 01:26
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Is ABCD a square ?

1. ABCD is a trapezium.
2. ABCD is not a rhombus.

I chose "D". My explanation goes like this.

1. If ABCD is a trapezium then it can never be a square. So this is SUFF.

2. ABCD is not a rhombus. This also implies that ABCD can never be a square ( All squares are rhombus but all rhombus are not squares ). --SUFF

But the answer is not D. (Source - MBA quantitative aptitude -- McGraw Hills Publication)

Am I missing something. Would like to know your responses.

Thanks
VP
Joined: 25 Nov 2004
Posts: 1483
Re: DS -- square vs rhombus [#permalink]

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28 Jul 2006, 06:54
jainvik7 wrote:
Is ABCD a square ?

1. ABCD is a trapezium.
2. ABCD is not a rhombus.

I chose "D". My explanation goes like this.

1. If ABCD is a trapezium then it can never be a square. So this is SUFF.

2. ABCD is not a rhombus. This also implies that ABCD can never be a square ( All squares are rhombus but all rhombus are not squares ). --SUFF

But the answer is not D. (Source - MBA quantitative aptitude -- McGraw Hills Publication)

Am I missing something. Would like to know your responses.

Thanks

agree with you. there is no reason that 2 doesnot work. if abcd is not a rhomus, it is not a square cuz square a special type of rhobus. the given quadilateral can be a ractangle but cannot be a square.

D is it.
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Joined: 20 Nov 2005
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Schools: Completed at SAID BUSINESS SCHOOL, OXFORD - Class of 2008

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28 Jul 2006, 08:16
Should be D.

Whats the explanation in the book?
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SAID BUSINESS SCHOOL, OXFORD - MBA CLASS OF 2008

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Joined: 22 May 2006
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28 Jul 2006, 09:04
Guys, it's B.
Attachments

quadril.jpg [ 67.39 KiB | Viewed 1069 times ]

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Intern
Joined: 23 Jul 2006
Posts: 49

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28 Jul 2006, 09:25

Statm1: Insuff

Statm2: NO all the rhombuses are squares.....for that reason what happen if I am taking one of that rhombuses..I dont know if ABCD is a square. Insuff

E

..?????????

..
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Joined: 22 May 2006
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28 Jul 2006, 09:28
zorro13 wrote:

Statm1: Insuff

Statm2: NO all the rhombuses are squares.....for that reason what happen if I am taking one of that rhombuses..I dont know if ABCD is a square. Insuff

..

All squares are rhombuses.
ABCD is not a rhombus. then ABCD is not a square
Thus, S2 is sufficient.
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Joined: 14 Mar 2006
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28 Jul 2006, 10:16
I also go with D.

a square or a rectangle is a type of rhombus.
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Joined: 23 Jul 2006
Posts: 49

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28 Jul 2006, 10:54
freetheking wrote:
zorro13 wrote:

Statm1: Insuff

Statm2: NO all the rhombuses are squares.....for that reason what happen if I am taking one of that rhombuses..I dont know if ABCD is a square. Insuff

..

All squares are rhombuses.
ABCD is not a rhombus. then ABCD is not a square
Thus, S2 is sufficient.

......oh yes....you are right....thanks...
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28 Jul 2006, 11:13
Which definition of trapezium to consider?
American: quadrilateral with no parallel sides
British: quadrilateral with two sides parallel

http://mathworld.wolfram.com/Trapezium.html

What is the source of this question??? If source of this question is British then answer is B. If source is American then answer is D. I think GMAT prefers American standards? What you guys think???
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28 Jul 2006, 11:18
ps_dahiya wrote:
Which definition of trapezium to consider?
American: quadrilateral with no parallel sides
British: quadrilateral with two sides parallel

http://mathworld.wolfram.com/Trapezium.html

What is the source of this question??? If source of this question is British then answer is B. If source is American then answer is D. I think GMAT prefers American standards? What you guys think???

Interesting point..
I assumed that the trapezium is equal to the trapezoid.
http://mathworld.wolfram.com/Trapezoid.html

I think there's no controversial concept in quant section of GMAT.
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28 Jul 2006, 12:20
its ok that trapiziods are quadilaterals but i donot think trapiziods are square/rectangle/rhombus. trapizoids are a special case where two sides are ll other two are not.
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28 Jul 2006, 12:42
MA wrote:
trapizoids are a special case where two sides are ll other two are not.

Red part is wrong.
Definition of a trapzoid : a trapezoid is a quadrilateral with two sides parallel.
Thus, every parallelogram is a trapezoid by the definition of a trapezoid.
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28 Jul 2006, 13:20
freetheking wrote:
MA wrote:
trapizoids are a special case where two sides are ll other two are not.

Red part is wrong.
Definition of a trapzoid : a trapezoid is a quadrilateral with two sides parallel.
Thus, every parallelogram is a trapezoid by the definition of a trapezoid.

i donot think that your statement is correct. i never saw that any trapizoid that is also parallogram. could you show a trapizoid figure?

trapezoid is a special case of quadilatral where the opposit two sides are parallel while the other two sides are not.
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28 Jul 2006, 13:45
Ma, I think it's controversial..

http://en.wikipedia.org/wiki/Trapezoid
Some authors define it as a quadrilateral having exactly one pair of parallel sides, so as to exclude parallelograms.
but some are not.

A trapezoid is a quadrilateral 'only' two of whose sides are parallel to each other. (In some European countries and Korea, a trapezoid is defined as a quadrilateral two or more of whose sides are parallel to each other. By this definition, a parallelogram is also a trapezoid.)
http://www.wikinfo.org/wiki.php?title=Trapezoid

I grew up in Korea. maybe that's why making it issue....
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Joined: 26 Jun 2006
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28 Jul 2006, 20:04
Wow, such a lively discussion!

I selected (B) in seconds and was 100% sure I was right. And then I started reading other people's answers... I never knew about differences of opinion on simple geometric facts like this one. I guess I should be more open minded next time.

(The answer is still (B), by the way, as I am from the Old World )
VP
Joined: 25 Nov 2004
Posts: 1483

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28 Jul 2006, 23:24
freetheking wrote:
Ma, I think it's controversial..

http://en.wikipedia.org/wiki/Trapezoid
Some authors define it as a quadrilateral having exactly one pair of parallel sides, so as to exclude parallelograms.
but some are not.

A trapezoid is a quadrilateral 'only' two of whose sides are parallel to each other. (In some European countries and Korea, a trapezoid is defined as a quadrilateral two or more of whose sides are parallel to each other. By this definition, a parallelogram is also a trapezoid.)
http://www.wikinfo.org/wiki.php?title=Trapezoid

I grew up in Korea. maybe that's why making it issue....

oh its interesting to know that trapizoids are taught differently in korea. thanks for sharing.

but, imo, in terms of gmat, trapizoid is not considered rhombus/square/ractangle.
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28 Jul 2006, 23:27
MA wrote:
but, imo, in terms of gmat, trapizoid is not considered rhombus/square/ractangle.

Agreed. I never thought a definition can be different in some countries.
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28 Jul 2006, 23:27
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