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GmatKiss: Legendary Member; Posts: 2789; Joined: Tue Jul 26, 2011 12:19 am; Location: Chennai, India; Thanked: 206 times; Followed by:43 members; GMAT Score:640

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by GmatKiss » Sat Oct 22, 2011 2:17 am

Please refer attachment!

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Source: Beat The GMAT — Data Sufficiency | Sat Oct 22, 2011 2:17 am

shankar.ashwin: Legendary Member; Posts: 966; Joined: Sat Jan 02, 2010 8:06 am; Thanked: 230 times; Followed by:21 members

by shankar.ashwin » Sat Oct 22, 2011 2:30 am

A IMO

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Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pm; Location: Milpitas, CA; Thanked: 1854 times; Followed by:523 members; GMAT Score:770

by Anurag@Gurome » Sat Oct 22, 2011 3:20 am

From the figure, it is not very clear whether x is the measure of angle ACB or of angle ACD.

If x is the measure of angle ACB, then statement 1 is sufficient only as y and x are the measures of alternate interior angles. Hence, x = y = 50

The correct answer will be A.

But if x is the measure of angle ACD, then statement none of the statements are individually sufficient. Only both statements together we can determine the value of x as (180 - y - z) = (180 - 90) = 90

The correct answer will be C.

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rahulvsd: Master | Next Rank: 500 Posts; Posts: 184; Joined: Tue Sep 07, 2010 9:43 am; Thanked: 6 times; Followed by:1 members

by rahulvsd » Sat Oct 22, 2011 9:20 am

If ACD is x, then A can still be sufficient. As ACD and CAD are interior angles on the same side of the transversal and they are supplementary.

So answer is A, even if x is angle ACD.

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Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pm; Location: Milpitas, CA; Thanked: 1854 times; Followed by:523 members; GMAT Score:770

by Anurag@Gurome » Sat Oct 22, 2011 10:05 am

rahulvsd wrote:If ACD is x, then A can still be sufficient. As ACD and CAD are interior angles on the same side of the transversal and they are supplementary.

Refer to the following diagram,

Angle ACO and angle CAD are interior angles on the same side of the transversal and they are supplementary not angle ACD and angle CAD.

A simple fact that you've ignored:
angle ACD and angle CAD are the two angles of same triangle. If they are supplementary, then their sum will be equal to 180 degrees. That means the measure of the third angle, i.e. angle ADC will be zero. This in turn means the point D will lie on the line segment AC, which is not possible according to the figure given.

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rahulvsd: Master | Next Rank: 500 Posts; Posts: 184; Joined: Tue Sep 07, 2010 9:43 am; Thanked: 6 times; Followed by:1 members

by rahulvsd » Sat Oct 22, 2011 10:33 am

Thanks a lot Anurag. Will be more careful here on.

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