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Re: geometry problem [#permalink]
09 Jun 2010, 10:28

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.

Re: geometry problem [#permalink]
09 Jun 2010, 11:07

Expert's post

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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Re: geometry problem [#permalink]
09 Jun 2010, 22:49

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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Re: geometry problem [#permalink]
13 Oct 2013, 14:41

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?

Re: geometry problem [#permalink]
13 Oct 2013, 14:48

Expert's post

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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