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If the length of side AB is 17, is triangle ABC a right [#permalink]
 24 Jul 2007, 19:06
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If the length of side AB is 17, is triangle ABC a right triangle?
(1) The length of side BC is 144.
(2) The length of side AC is 145.
Can someone explain what would be correct answer for this?
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Intern
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Can this be even be a triangle?
I may be wrong but my answer is E.
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Director
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a3d wrote: If the length of side AB is 17, is triangle ABC a right triangle?
(1) The length of side BC is 144.
(2) The length of side AC is 145.
Can someone explain what would be correct answer for this?
This was a good one .
Instead of calculating squares ( which gmat will never ask you ) , I did a quick calculation ie 145^2 - 144^2 = (145-144)(145 +144 ) = 289
which is square of 17.
So it does means a triangle with 17 144 145 is right angle triangle . But this does not mean that answer is C . But now if we know that one of side 144 or 145 it has to be a right angle triangle .
So answer is D
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Intern
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Statement 1 Insuff
Statement 2 Insuff
Combining, is 17^2 +144^2=145^2?
for 2 consecutive mumbers, the difference in their squares= n1+n2
therefore 144^2-145^2=289=17^2
therefore the triangle has to be RtAng
Therefore c
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Senior Manager
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C
by knowing one side is 145 tells you nothing of the shape of the triangle.
For all we know it could be close to a straight line.
similar with option B
combine A and B and use pythogarus to see if it adds up.
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Senior Manager
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ashkrs wrote: a3d wrote: But this does not mean that answer is C . But now if we know that one of side 144 or 145 it has to be a right angle triangle .
So answer is D Why do u say that? My original answer was C. But I gave this a thought after reading ur answer but decided, just knowing two sides and no angles would be useless.
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Senior Manager
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ioiio wrote: ashkrs wrote: a3d wrote: But this does not mean that answer is C . But now if we know that one of side 144 or 145 it has to be a right angle triangle .
So answer is D Why do u say that? My original answer was C. But I gave this a thought after reading ur answer but decided, just knowing two sides and no angles would be useless. It is simply impossible to conclude on the type of a triangle by knowing just 2 sides. It has to be C
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Current Student
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It has to be C. And, to save time, there is no need to calculate if it is a right triangle or not.
1) Ins. - you know 2 sides, no angles
2) Ins. - same reasoning
Together you have 3 sides and it either follows the pythagreon theorem or doesn't. The answer doesn't matter if its yes or no, just if it can be solved.
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Senior Manager
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emoryhopeful wrote: It has to be C. And, to save time, there is no need to calculate if it is a right triangle or not.
1) Ins. - you know 2 sides, no angles
2) Ins. - same reasoning
Together you have 3 sides and it either follows the pythagreon theorem or doesn't. The answer doesn't matter if its yes or no, just if it can be solved.
ah. the more of these I read the more these make sense.
I was leaning to E becasue of the lack of angles.
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emoryhopeful wrote: It has to be C. And, to save time, there is no need to calculate if it is a right triangle or not.
1) Ins. - you know 2 sides, no angles
2) Ins. - same reasoning
Together you have 3 sides and it either follows the pythagreon theorem or doesn't. The answer doesn't matter if its yes or no, just if it can be solved.
Great answer! I need to remember that for a DS all you need to know is whether or not you can solve it (or answer the yes/no question). The less actual math to do, the better!
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Director
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I agree with ashkrs
This is a righ angle triangle
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I'm inclinced to take C here, because you don't know the shape of a triangle with just one side given.
With both, you can quickly test if it fits pythagora's theorem.
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a3d wrote: If the length of side AB is 17, is triangle ABC a right triangle?
(1) The length of side BC is 144.
(2) The length of side AC is 145.
Can someone explain what would be correct answer for this?
I get C as well. No calculation needed.. just definition/rules of triangles.
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