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

It is currently 20 Oct 2014, 05:11

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

If quadrilateral ABCD is inscribed into a circumference

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Senior Manager
Senior Manager
User avatar
Joined: 13 Mar 2007
Posts: 296
Location: Russia, Moscow
Followers: 2

Kudos [?]: 21 [0], given: 0

If quadrilateral ABCD is inscribed into a circumference [#permalink] New post 29 Aug 2007, 04:32
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
E. If quadrilateral ABCD is inscribed into a circumference. What is the value of angle A?

(1) AC=CD
(2) angle D=70 degrees

Please, explanations ONLY
Manager
Manager
avatar
Joined: 14 Jan 2007
Posts: 170
Followers: 2

Kudos [?]: 7 [0], given: 0

 [#permalink] New post 29 Aug 2007, 05:49
I dont understand what circumference means i am assuming that a quad is inscirbed in a circle.
I think answer should be C

if ac=cd
then tri(acd) is isosceles and ang adc= ang cad

and if the quadialteral is inscribed in circle then b shud make it a parallelogram. therefore, ab=cd=ac and ang cad =ang cab= ang abc

and ang acd =ang cab

and ang A = ang dac+ ang cab

and we need to know atleast one of these angles
which is provided in stmt 2

hence we need both the stmts

I am not sure whether any other type of quad ( other than llgm ) can be inscribed in the circle with ac=cd
CEO
CEO
User avatar
Joined: 29 Mar 2007
Posts: 2593
Followers: 16

Kudos [?]: 197 [0], given: 0

Re: DS (quadrilateral) [#permalink] New post 29 Aug 2007, 08:08
Vlad77 wrote:
E. If quadrilateral ABCD is inscribed into a circumference. What is the value of angle A?

(1) AC=CD
(2) angle D=70 degrees

Please, explanations ONLY


Don't try this in your head. Draw it on paper. Ok i think i did it right...

A quadrilateral is ANY 4 sided polygon I.E a sqaure, rectangle, rhombus, trapezoid etc...

S1: AC=CD, well ok 2 sides are equal, but what about the other two sides... This doesn't really help us w/ the actual angle. Insuff,

S2: angle D=70degres... This tells us about angle D, but gives us no clue to what angle A is. Insuff.

S1 and S2: To me both of these are still insuff. The 4sided polygon can be drawn in almost an infinite amount of ways, as long as AC=CD and D is 70degrees. However, when drawing the quad. It is easy to see that A could be several different values while satisfying S1 and S2.

Now b/c its inscribed in the circle... Im not sure if I missed something here, or if there is a special rule.

Anyway my ans is E
Manager
Manager
avatar
Joined: 14 Jan 2007
Posts: 170
Followers: 2

Kudos [?]: 7 [0], given: 0

 [#permalink] New post 29 Aug 2007, 11:26
how do u know that ac cd are sides ...not a diagonal and one side...?
Director
Director
avatar
Joined: 22 Aug 2007
Posts: 573
Followers: 1

Kudos [?]: 13 [0], given: 0

Re: DS (quadrilateral) [#permalink] New post 30 Aug 2007, 21:01
Vlad77 wrote:
E. If quadrilateral ABCD is inscribed into a circumference. What is the value of angle A?

(1) AC=CD
(2) angle D=70 degrees

Please, explanations ONLY


Let me try,

I got E

I would add one thing to the definiton blackbelt gave; the sum of the angles of quadrilateral is 360.

1- stm, say two sides are equal, so we can draw an isoceles and the sum of its angles wil be 180 degree. That is BAC+ABC+BCA. So for the second part of the quadrilateral we still have 180 degrees. That is CAD+ADC+ACD, hundreds possibilities...inluding right isoceles.
Please, draw. And you will see that A=BAC+CAD; C= BCA+ACD.
We need A, here, so as long as BAC or CAD vary we can not find exact value of A. Evethough drawing an asoceles ABC helps us to fix BAC, we can not say the same about CAD, cuz, again, 180 degrees can be distributed among 3 angles in a number of ways.

2-stm, says that D is 70 degrees, this leaves us with 290 degrees for the rest 3 angles, again hundrens of combinations.

Both,
Ok, from 1st we can assume ABC is fixed now, BAC = BCA are fixed angles, leaving us with 180 degrees for the second part,second statement says that CAD + ACD =180 -70=110, again leaving number of possible angles for CAD and ACD. Could be 50 and 60, or vise versa, and that in turn effects A, which is BAC +CAD.

Look, even if we make such assumptions that line AC -diagonal of ABCD is diameter, there are still hundreds of possible A angles.

That was my reasoning...I still am curious about other possible approaches for this problem.
Re: DS (quadrilateral)   [#permalink] 30 Aug 2007, 21:01
    Similar topics Author Replies Last post
Similar
Topics:
1 ABCD is the inscribed quadrilateral in the given circle guerrero25 1 17 Jun 2013, 12:17
14 Experts publish their posts in the topic Quadrilateral ABCD is inscribed in circle K. The diameter of bhandariavi 16 05 Feb 2011, 17:04
Quadrilateral ABCD is inscribed into a circle. What is the study 3 29 Oct 2008, 22:57
Quadrilateral ABCD is inscribed into a circle. What is the amitdgr 1 06 Oct 2008, 00:43
If a quadrilateral ABCD is inscribed into a circumference. {I} 1 30 Apr 2007, 01:31
Display posts from previous: Sort by

If quadrilateral ABCD is inscribed into a circumference

  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®.