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# Is the triangle with three sides a, b, c, isosceles?

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Manager
Joined: 05 Mar 2010
Posts: 217
Is the triangle with three sides a, b, c, isosceles? [#permalink]

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09 Jun 2010, 11:18
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Question Stats:

49% (01:27) correct 51% (00:23) wrong based on 153 sessions

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Is the triangle with three sides a, b, c, isosceles?

(1) a = b
(2) c ≠ b

OA will be posted later
[Reveal] Spoiler: OA

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Last edited by Bunuel on 20 Jun 2013, 04:56, edited 1 time in total.
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09 Jun 2010, 11:28
IMO C

A alone is INSUFFICIENT. Given a=b, but we do not know anything about c. If c=a, then it is equilateral.
B alone is INSUFFICIENT. Given c≠b, we know nothing about 'a' here.

A and B together - SUFFICIENT.
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Joined: 02 Sep 2009
Posts: 39678

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09 Jun 2010, 12:07
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hardnstrong wrote:
Is the triangle with three sides a,b,c, isosceles?
(1) a = b
(2) c ≠ b

OA will be posted later

sjayasa wrote:
IMO C

A alone is INSUFFICIENT. Given a=b, but we do not know anything about c. If c=a, then it is equilateral.
B alone is INSUFFICIENT. Given c≠b, we know nothing about 'a' here.

A and B together - SUFFICIENT.

This cannot be the real GMAT question as it test technicality of defining isosceles triangle:
If we say that an isosceles triangle is a triangle with exactly two equal sides then the answer is C.
If we say that an isosceles triangle is a triangle with at least two equal sides then answer is A. So if we take this definition (which is more precise and more common) then we'll have that equilateral triangle is just a special case of isosceles triangle.

If I had to pick I'd pick A for this question.
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09 Jun 2010, 13:51
I thinks the answer should be A.
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Joined: 05 Mar 2010
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09 Jun 2010, 23:49
OA is A

i found this question in one of the good sources of questions in GMAT found on other website
Though the question is with diagram of a triangle with three sides given as a,b,c

stmt 1. Explanation there says that because a=b hence it is an isosceles triangle (what about c , we dont know if c is equal to a or b, or not)

It says stmt 2 is insufficient because c is not equal to b (if in statement1 we didnt consider c then why to consider a in statment 2)

Answer itself contradicts each other. Thats why i posted it here to get to know if i am missing something
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13 Oct 2013, 15:41
Bunuel wrote:
hardnstrong wrote:
Is the triangle with three sides a,b,c, isosceles?
(1) a = b
(2) c ≠ b

OA will be posted later

sjayasa wrote:
IMO C

A alone is INSUFFICIENT. Given a=b, but we do not know anything about c. If c=a, then it is equilateral.
B alone is INSUFFICIENT. Given c≠b, we know nothing about 'a' here.

A and B together - SUFFICIENT.

This cannot be the real GMAT question as it test technicality of defining isosceles triangle:
If we say that an isosceles triangle is a triangle with exactly two equal sides then the answer is C.
If we say that an isosceles triangle is a triangle with at least two equal sides then answer is A. So if we take this definition (which is more precise and more common) then we'll have that equilateral triangle is just a special case of isosceles triangle.

If I had to pick I'd pick A for this question.

Hi Bunuel, thanks for pointing it out.
What does GMAT say about isosceles/equilateral definition? Is there a common agreement?
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Joined: 02 Sep 2009
Posts: 39678

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13 Oct 2013, 15:48
jlgdr wrote:
Bunuel wrote:
hardnstrong wrote:
Is the triangle with three sides a,b,c, isosceles?
(1) a = b
(2) c ≠ b

OA will be posted later

sjayasa wrote:
IMO C

A alone is INSUFFICIENT. Given a=b, but we do not know anything about c. If c=a, then it is equilateral.
B alone is INSUFFICIENT. Given c≠b, we know nothing about 'a' here.

A and B together - SUFFICIENT.

This cannot be the real GMAT question as it test technicality of defining isosceles triangle:
If we say that an isosceles triangle is a triangle with exactly two equal sides then the answer is C.
If we say that an isosceles triangle is a triangle with at least two equal sides then answer is A. So if we take this definition (which is more precise and more common) then we'll have that equilateral triangle is just a special case of isosceles triangle.

If I had to pick I'd pick A for this question.

Hi Bunuel, thanks for pointing it out.
What does GMAT say about isosceles/equilateral definition? Is there a common agreement?

According to the OG an isosceles triangle has at least two sides of the same length.

As for equilateral triangle: equilateral triangle is a triangle which has all sides of the same length.
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Re: Is the triangle with three sides a, b, c, isosceles? [#permalink]

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17 Sep 2016, 12:16
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Re: Is the triangle with three sides a, b, c, isosceles?   [#permalink] 17 Sep 2016, 12:16
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