2 intesecting lines..

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shipra: Senior | Next Rank: 100 Posts; Posts: 74; Joined: Mon May 26, 2008 11:23 pm; Location: Dubai; Thanked: 6 times

by shipra » Sat Jun 21, 2008 12:27 am

Two intersecting lines form four angles. Are the lines perpendicular?

(1) Each of the angles is equal to exactly one of the other three angles.

(2) The sum of three angles does NOT equal to 270 degrees.

A) Statement (1) BY ITSELF is sufficient to answer the question, but statement (2) by itself is not.

B) Statement (2) BY ITSELF is sufficient to answer the question, but statement (1) by itself is not.

C) Statements (1) and (2) TAKEN TOGETHER are sufficient to answer the question, even though NEITHER statement BY ITSELF is sufficient.

D) Either statement BY ITSELF is sufficient to answer the question.

E) Statements (1) and (2) TAKEN TOGETHER are NOT sufficient to answer the question, meaning that further information would be needed to answer the question.

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Source: Beat The GMAT — Data Sufficiency | Sat Jun 21, 2008 12:27 am

atlantic: Master | Next Rank: 500 Posts; Posts: 132; Joined: Sun Apr 27, 2008 10:31 am; Location: Portugal; Thanked: 7 times

by atlantic » Sat Jun 21, 2008 4:58 am

Hi,

Not sure about what is the correct answer but I would bet on B.

Let me explain why.

(1) we get nothing at all. It only says that anyone of the angles has another one with the same degree, but not that all the angles are equal - which is necessary to say that the lines are perpendicular. INSUFF

(2) the lines are only perpendicular if all the angles are equal, being all 90º. Here it says that the sum of any three angles cannot be equal to 270º and therefore, angles are not 90º angles. SUFF.

Hope it helps. Do you have the OA.

BTW: it took me less than 2min.

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albertrahul: Senior | Next Rank: 100 Posts; Posts: 83; Joined: Wed Jun 04, 2008 3:30 am; Thanked: 4 times

by albertrahul » Sat Jun 21, 2008 5:16 am

I second Atlantic, my vote goes for B as well.

What is OA?

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durgesh79: Master | Next Rank: 500 Posts; Posts: 167; Joined: Tue Apr 22, 2008 12:48 am; Thanked: 15 times

by durgesh79 » Sat Jun 21, 2008 6:29 am

its D

statement 1 : Each of the angles is equal to exactly one of the other three angles.

if the lines were perpedicular, then each of the sangle would have been equal to all other 3 angles ... if t is known that each of the angle is equal to exactly one of the other three ... we can say that the lines are not perpendicular ...... ans we have to answer YES or NO .....

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atlantic: Master | Next Rank: 500 Posts; Posts: 132; Joined: Sun Apr 27, 2008 10:31 am; Location: Portugal; Thanked: 7 times

by atlantic » Sat Jun 21, 2008 7:11 am

Guess you're correct durgesh.

Only if 'exactly' was replaced by 'at least' would (1) not be enough.

I should read statements more carefully. Again this is one of the competences tested by GMAT.

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shipra: Senior | Next Rank: 100 Posts; Posts: 74; Joined: Mon May 26, 2008 11:23 pm; Location: Dubai; Thanked: 6 times

by shipra » Sat Jun 21, 2008 8:34 pm

OA is D....even i went fr B....i kind of agree wid atlantic...how is the first statement Sufficient?

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albertrahul: Senior | Next Rank: 100 Posts; Posts: 83; Joined: Wed Jun 04, 2008 3:30 am; Thanked: 4 times

by albertrahul » Sun Jun 22, 2008 2:13 am

Well first sentence tells us that each angle is equal to ONLY ONE other angle. This information is sufficient to answer question that is asked, "Are these two lines perpendicular?"
For two lines to be perpendicular each angle should equal other Three angles.

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g_beatthegmat: Master | Next Rank: 500 Posts; Posts: 100; Joined: Fri Jul 27, 2007 12:36 pm; Thanked: 6 times

by g_beatthegmat » Sun Jun 22, 2008 7:08 am

(D).

Both are sufficient as durgesh79 mentioned above because of the following reasons -

i) Each of the angles is equal to exactly one of the other three angles.
If the lines were perpendicular to each other, all the angles would have been equal to 90 degrees. But the statement says each of the angles is equal to just ONE other angle, and that's obviously the corresponding vertical angles.

Hence sufficient.

ii) The sum of 3 angles is NOT 270.
If the lines were perpendicular, sum of any 3 angles would have been = 270.

Hence sufficient.

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