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DS - Triangle property- Need help

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by prat_agl » Fri Oct 14, 2011 6:04 pm
Is triangle ABC isoceles?
1. Angle B = 60 degrees
2. Angle C = 60

[spoiler]I think Answer is D.If one angle is 60 sum of remaining 2 angles is 120. Let's say second angle is also 60 so third will also be 60 making it Equilateral. It is not Isosceles. If 2nd is more than 60 third will be less than 60 and vice-versa making it scalene. It is a question from https://gmat.practice-tests.learnhub.com and it says correct ans is C. can anybody help me here [/spoiler]
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by n@resh » Fri Oct 14, 2011 6:59 pm
prat_agl wrote:Is triangle ABC isoceles?
1. Angle B = 60 degrees
2. Angle C = 60

[spoiler]I think Answer is D.If one angle is 60 sum of remaining 2 angles is 120. Let's say second angle is also 60 so third will also be 60 making it Equilateral. It is not Isosceles. If 2nd is more than 60 third will be less than 60 and vice-versa making it scalene. It is a question from https://gmat.practice-tests.learnhub.com and it says correct ans is C. can anybody help me here [/spoiler]
using stat1 and stat2, individually we can't answer the quesion as we don't know other angles!

From using both statements: 1 and 2;
B = C = 60. we can deduce that the triangle will be an Equilateral, as sum of the angles in a traingle will be 180, hence the other Angle A must be 60.
Note: An equilateral triangle is a special type of special isosceles triangle in which all three sides are congruent. Equilateral triangles are also equiangular, which means all three angles are congruent.

Nevertheless, answer for this question is C!
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by prat_agl » Fri Oct 14, 2011 9:28 pm
Hi N@resh,

Please have a look at the spoiler and let me know if you still think the same.
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by shankar.ashwin » Fri Oct 14, 2011 10:00 pm
Just a thought,

An isosceles triangle is one which has at least 2 sides equal and not exactly 2 sides equal.

So as naresh pointed, an isosceles triangle could also be an equilateral triangle.
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by Brent@GMATPrepNow » Sat Oct 15, 2011 6:38 am
shankar.ashwin wrote:Just a thought,

An isosceles triangle is one which has at least 2 sides equal and not exactly 2 sides equal.

So as naresh pointed, an isosceles triangle could also be an equilateral triangle.
Exactly!
Quote from the Official Guide: "An isosceles triangle has at least two sides of the same length."

So, an equilateral triangle is a type of isosceles triangle.
Just like a square is a type of rectangle.

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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by prat_agl » Sat Oct 15, 2011 6:53 am
Thanks all. Now it make more sense!!!
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by saketk » Mon Oct 17, 2011 8:01 pm
shankar.ashwin wrote:Just a thought,

An isosceles triangle is one which has at least 2 sides equal and not exactly 2 sides equal.

So as naresh pointed, an isosceles triangle could also be an equilateral triangle.
Yeah that's the standard defination
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