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Why the answer is D

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Why the answer is D

by joshi.komal » Tue Jan 22, 2008 5:56 am
Is quadrilateral ABCD a rhombus?

(1) Line segments AC and BD are perpendicular bisectors of each other.

(2) AB = BC = CD = AD


I am not sure why stmt 2 is sufficient... Can anyone explain

Thanks
Komal
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by sankruth » Tue Jan 22, 2008 6:06 am
St 1: SUFF
If diagonals are perpendicular bisectors of each other then fugure is a Square or Rhombus.

St2 : SUFF
If 4 sides are equal, then figure must be a square or rhombus. Square is Rhombus where both diagonals have equal length and are perpendicular bisectors of each other

So, D. Hope that helps!
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by Stuart@KaplanGMAT » Tue Jan 22, 2008 6:33 am
A rhombus is a parallelogram with 4 equal sides. A square is just a special kind of rhombus (just like a square is a special kind of rectangle).

So, if we have a 4 sided shape with equal sides, it falls within the definition of a rhombus.
Last edited by Stuart@KaplanGMAT on Wed Jan 23, 2008 12:13 pm, edited 1 time in total.
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by preciousrain7 » Wed Jan 23, 2008 11:47 am
Stuart Kovinsky wrote:A rhombus is a parallelogram with 4 equal sides. A square is just a special kind of rhombus (just like a square/rhombus is a special kind of rectangle).

So, if we have a 4 sided shape with equal sides, it falls within the definition of a rhombus.
Stuart,

is it safe to say, a sq can be a rhombus but a rhombus can't be a square and a sq./rhombus can be a rectangle but a rect. can't be a sq./rhombus?

Sonia
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by Stuart@KaplanGMAT » Wed Jan 23, 2008 12:12 pm
preciousrain7 wrote:
Stuart Kovinsky wrote:A rhombus is a parallelogram with 4 equal sides. A square is just a special kind of rhombus (just like a square is a special kind of rectangle).

So, if we have a 4 sided shape with equal sides, it falls within the definition of a rhombus.
Stuart,

is it safe to say, a sq can be a rhombus but a rhombus can't be a square and a sq./rhombus can be a rectangle but a rect. can't be a sq./rhombus?

Sonia
Not quite. Here's what we can say:

A square IS a rhombus.
A rhombus MAY BE a square.

A square IS a rectangle.
A rectangle MAY BE a square.

(I misstated the rhombus/rectangle relationship in my original post and have edited it - a rhombus isn't a rectangle, since all rectangles have 4 * 90 degree angles; a rectangle can be a rhombus, but only if it's also a square.)
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by preciousrain7 » Wed Jan 23, 2008 2:25 pm
Stuart Kovinsky wrote:
Stuart,

is it safe to say, a sq can be a rhombus but a rhombus can't be a square and a sq./rhombus can be a rectangle but a rect. can't be a sq./rhombus?

Sonia
Not quite. Here's what we can say:

A square IS a rhombus.
A rhombus MAY BE a square.

A square IS a rectangle.
A rectangle MAY BE a square.

(I misstated the rhombus/rectangle relationship in my original post and have edited it - a rhombus isn't a rectangle, since all rectangles have 4 * 90 degree angles; a rectangle can be a rhombus, but only if it's also a square.)[/quote]

Thank you.
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