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Is AB parallel to CD?

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Source: — Data Sufficiency |
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Re: Is AB parallel to CD?

by vittalgmat » Sat Jul 18, 2009 12:15 am
madhur_ahuja wrote:Is AB parallel to CD?
(1) Angle a + angle b = 180º
(2) angle a + angle c + angle d + angle e = 360º
Pls post the OA within spoilers.


thanks
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by adamsmith2009 » Sat Jul 18, 2009 7:44 pm
D

Both statements are sufficient
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by PussInBoots » Sat Jul 18, 2009 7:58 pm
Sorry for offtopic, testing RSS feed filter
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by madhur_ahuja » Sat Jul 18, 2009 9:18 pm
adamsmith2009 wrote:D

Both statements are sufficient

How is I sufficient ?

IMO its B.
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by zenithexe » Sat Jul 18, 2009 9:45 pm
i agree with madhur, please look at the pic, that's perfectly valid considering the statement 1)
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by viju9162 » Sun Jul 19, 2009 12:40 am
How B is sufficient to answer the question ?
"Native of" is used for a individual while "Native to" is used for a large group
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Re: Is AB parallel to CD?

by tohellandback » Sun Jul 19, 2009 2:12 am
madhur_ahuja wrote:Is AB parallel to CD?
(1) Angle a + angle b = 180º
(2) angle a + angle c + angle d + angle e = 360º
IMO B
1) the two lines will be parallel when angle a+ angle c=180. (property)
angle c=180-angle b
when b=90, the lines are parallel, but in all other cases lines are not parallel.
NOT SUFF

2)angle a + angle c + angle d + angle e = 360º
angle d+ angle e=180
angle a + angle c=180
SUFF
The powers of two are bloody impolite!!
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by viju9162 » Sun Jul 19, 2009 5:33 am
angle a + angle c = 180. Could you please explain this property which you have used to derive?

However, as I know, these are alternate angles and as per parallel lines property, when a transversal cuts the parallel lines, they form two pair of alternate angles.

How are we assuming these angles are supplementary?
"Native of" is used for a individual while "Native to" is used for a large group
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by tohellandback » Sun Jul 19, 2009 6:09 am
viju9162 wrote:angle a + angle c = 180. Could you please explain this property which you have used to derive?

However, as I know, these are alternate angles and as per parallel lines property, when a transversal cuts the parallel lines, they form two pair of alternate angles.

How are we assuming these angles are supplementary?
the property is "interior angles on the same side are supplementary"
plz check the image
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by saakshig » Sun Jun 21, 2015 9:49 pm
Option a)
Angle a + angle b = 180.
Also since we can see that for any situation, angle b + angle c will be 180. (On the same line, supplementary).
This angle a + angle b = angle b + angle c.
Thus angle a = angle c. These are alternate angles. If they are equal lines are parallel.
SUFFICIENT

Option b)
Angles a + c + d + e = 360
d + e = 180 (supplementary)
Thus a + c = 180
Case 1: a=c=90. Lines will be parallel.
Case 2: for any other 2 values of a and c, a will not equal c. Hence not parallel.
INSUFFICIENT.

Answer is A.
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