Find all School-related info fast with the new School-Specific MBA Forum

It is currently 16 Sep 2014, 22:02

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Algebra

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Senior Manager
Senior Manager
User avatar
Joined: 08 Nov 2010
Posts: 422
WE 1: Business Development
Followers: 7

Kudos [?]: 34 [0], given: 161

GMAT ToolKit User GMAT Tests User
Algebra [#permalink] New post 27 Aug 2011, 09:19
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

71% (02:41) correct 29% (00:00) wrong based on 14 sessions
Hey guys, I cannot understand OE for stat 1.
My opinion is different from OA, please find my mistake.

I have problem to confirm the ab is vertical to the lines.
thanks.
[Reveal] Spoiler: OA

Attachments

File comment: Question file
123.jpg
123.jpg [ 44.61 KiB | Viewed 1055 times ]


_________________

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Senior Manager
Senior Manager
User avatar
Joined: 08 Nov 2010
Posts: 422
WE 1: Business Development
Followers: 7

Kudos [?]: 34 [0], given: 161

GMAT ToolKit User GMAT Tests User
Re: Algebra [#permalink] New post 27 Aug 2011, 09:23
Not sure how to add this in a hide mode, this is the OA

#

1. Since EC = 2AC, EA = CA, EC = 2(6) = 12 and line AB is an angle bisector of angle EBC. This means that angle ABC = angle ABE. Since we know that angle ABC = 30, we know that angle ABE = 30. Further, since lines L and M are parallel, we know that line AB is perpendicular to line EC, meaning angle BAC is 90.
2. Since all the interior angles of a triangle must sum to 180:
angle ABC + angle BCA + angle BAC = 180
30 + angle BCA + 90 = 180
angle BCA = 60
3. Since all the interior angles of a triangle must sum to 180:
angle BCA + angle ABC + angle ABE + angle AEB = 180
60 + 30 + 30 + angle AEB = 180
angle AEB = 60
4. This means that triangle BCA is an equilateral triangle.
5. To find the area of triangle BCE, we need the base (= 12 from above) and the height, i.e., line AB. Since we know BC and AC and triangle ABC is a right triangle, we can use the Pythagorean theorem on triangle ABC to find the length of AB.
62 + (AB)2 = 122
AB2 = 144 - 36 = 108
AB = 1081/2
6. Area = .5bh
Area = .5(12)(1081/2) = 6*1081/2
7. Statement (1) is SUFFICIENT

# Evaluate Statement (2) alone.

1. The sum of the interior angles of any triangle must be 180 degrees.
DCG + GDC + CGD = 180
60 + 30 + CGD = 180
CGD = 90
Triangle CGD is a right triangle.
2. Using the Pythagorean theorem, DG = 1081/2
(CG)2 + (DG)2 = (CD)2
62 + (DG)2 = 122
DG = 1081/2
3. At this point, it may be tempting to use DG = 1081/2 as the height of the triangle BCE, assuming that lines AB and DG are parallel and therefore AB = 1081/2 is the height of triangle BCE. However, we must show two things before we can use AB = 1081/2 as the height of triangle BCE: (1) lines L and M are parallel and (2) AB is the height of triangle BCE (i.e., angle BAC is 90 degrees).
4. Lines L and M must be parallel since angles FDG and CGD are equal and these two angles are alternate interior angles formed by cutting two lines with a transversal. If two alternate interior angles are equal, we know that the two lines that form the angles (lines L and M) when cut by a transversal (line DG) must be parallel.
5. Since lines L and M are parallel, DG = the height of triangle BCE = 1081/2. Note that it is not essential to know whether AB is the height of triangle BCE. It is sufficient to know that the height is 1081/2. To reiterate, we know that the height is 8 since the height of BCE is parallel to line DG, which is 1081/2.
6. Since we know both the height (1081/2) and the base (CE = 12) of triangle BCE, we know that the area is: .5*12*1081/2 = 6*1081/2
7. Statement (2) alone is SUFFICIENT.

# Since Statement (1) alone is SUFFICIENT and Statement (2) alone is SUFFICIENT, answer D is correct.

_________________

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Intern
Intern
avatar
Status: Juggling Kid, wife, 2 bosses, and 15 clients
Joined: 13 May 2011
Posts: 15
Location: Jacksonville, FL
Schools: H W S
WE 1: 2 years IT
WE 2: 7 years IT Management
Followers: 0

Kudos [?]: 2 [0], given: 6

Re: Algebra [#permalink] New post 27 Aug 2011, 20:49
I see more assumptions than statements in the following part

and line AB is an angle bisector of angle EBC. This means that angle ABC = angle ABE. Since we know that angle ABC = 30, we know that angle ABE = 30. Further, since lines L and M are parallel, we know that line AB is perpendicular to line EC, meaning angle BAC is 90.
_________________

MGMAT1 Q48 V35 680
PR1 Q44 V37 660
PR2 Q51 V31 660
PR3 Q51 V37 710
PR4 Q50 V37 700
PR5 Q51 V41 730
MGMAT2 Q49 V45 760
GMATPREP1 Q49 V43 730
GMATPREP2 Q49 V43 730
MGMAT3 Q51 V36 710
GMATPREP1 Q51 V34 690

Senior Manager
Senior Manager
User avatar
Joined: 08 Nov 2010
Posts: 422
WE 1: Business Development
Followers: 7

Kudos [?]: 34 [0], given: 161

GMAT ToolKit User GMAT Tests User
Re: Algebra [#permalink] New post 27 Aug 2011, 22:20
DeepGagan wrote:
I see more assumptions than statements in the following part

and line AB is an angle bisector of angle EBC. This means that angle ABC = angle ABE. Since we know that angle ABC = 30, we know that angle ABE = 30. Further, since lines L and M are parallel, we know that line AB is perpendicular to line EC, meaning angle BAC is 90.



Agreed. Point B can easily be shifted to the left and still comply with all the data, but the angle will not be 90.
_________________

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Senior Manager
Senior Manager
User avatar
Joined: 08 Nov 2010
Posts: 422
WE 1: Business Development
Followers: 7

Kudos [?]: 34 [0], given: 161

GMAT ToolKit User GMAT Tests User
Re: Algebra [#permalink] New post 29 Aug 2011, 05:50
Re: Algebra   [#permalink] 29 Aug 2011, 05:50
    Similar topics Author Replies Last post
Similar
Topics:
Experts publish their posts in the topic algebra amitgovin 2 07 Oct 2009, 20:01
Algebra milind1979 2 27 Apr 2009, 18:27
Algebra milind1979 3 25 Mar 2009, 22:04
Algebra ! chiragr 10 17 Jan 2006, 02:57
Display posts from previous: Sort by

Algebra

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.