NEW HERE? LEARN MORE
closeclose
Last visit was: 26 Apr 2024, 09:45 It is currently 26 Apr 2024, 09:45
Decision Tracker
My Rewards
New posts
New comers' posts

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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

What is the ratio of OA to AC? (1) OD is half the length of DC

SORT BY:
Date
Kudos
Tags:
Find Similar Topics 
Show Tags
Hide Tags
User avatar
L
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 92945
Own Kudos [?]: 619197 [3]
Given Kudos: 81609
Send PM
CAT Tests Forum Quiz Mode
What is the ratio of OA to AC? (1) OD is half the length of DC [#permalink] New post   18 Sep 2018, 22:02
3
Bookmarks
Expert Reply
00:00
A
B
C
D
E

Difficulty:

55% (hard)

Question Stats:

63% (02:19) correct 38% (02:47) wrong based on 80 sessions
Hide Show timer Statistics

What is the ratio of OA to AC? (Assume O is the center of the circle)

(1) OD is half the length of DC
(2) The area of ADC is 20.


Show Spoiler
Attachment:
image008.jpg
image008.jpg [ 3.19 KiB | Viewed 2200 times ]
ShowHide Answer
Official Answer
A
User avatar
D
PKN
Director
Director
Joined: 01 Oct 2017
Status:Learning stage
Posts: 827
Own Kudos [?]: 1300 [4]
Given Kudos: 41
WE:Supply Chain Management (Energy and Utilities)
Send PM
Re: What is the ratio of OA to AC? (1) OD is half the length of DC [#permalink] New post   21 Sep 2018, 04:47
2
Kudos
1
Bookmarks
Bunuel wrote:

What is the ratio of OA to AC?

(1) OD is half the length of DC
(2) The area of ADC is 20.


Show Spoiler
Attachment:
The attachment image008.jpg is no longer available


Question stem:- OA:AC=?

St1:- OD is half the length of DC

Please refer the enclosed diagram,

Radius, OC=OA=3x

Applying Pythagoras theorem in the triangle OAD, \(AD=2\sqrt{2}x\)
Again, Applying Pythagoras theorem in the triangle ADC, \(AC=2\sqrt{3}x\)

Now ratio of OA to AC can be determined.

Sufficient.

St2:- The area of ADC is 20.

No information is provided on the measure of AD and DC.

Insufficient.

Ans. (A)
Attachments

Circle ratio.PNG
Circle ratio.PNG [ 74.38 KiB | Viewed 1975 times ]

User avatar
L
GMATBusters
GMAT Tutor
Joined: 27 Oct 2017
Posts: 1905
Own Kudos [?]: 5582 [0]
Given Kudos: 236
WE:General Management (Education)
Send PM
GMAT ToolKit User
Re: What is the ratio of OA to AC? (1) OD is half the length of DC [#permalink] New post   23 Sep 2018, 01:01
Expert Reply
Bunuel, Do we have to consider that O is Center?
if O is not the center, it seems E

Bunuel wrote:

What is the ratio of OA to AC?

(1) OD is half the length of DC
(2) The area of ADC is 20.


Show Spoiler
Attachment:
image008.jpg
User avatar
D
PKN
Director
Director
Joined: 01 Oct 2017
Status:Learning stage
Posts: 827
Own Kudos [?]: 1300 [0]
Given Kudos: 41
WE:Supply Chain Management (Energy and Utilities)
Send PM
Re: What is the ratio of OA to AC? (1) OD is half the length of DC [#permalink] New post   23 Sep 2018, 01:05
I think we must consider point 'O' centre of the circle in the same way we do consider Angle ADC 90 degree.

Posted from my mobile device
User avatar
L
GMATBusters
GMAT Tutor
Joined: 27 Oct 2017
Posts: 1905
Own Kudos [?]: 5582 [0]
Given Kudos: 236
WE:General Management (Education)
Send PM
GMAT ToolKit User
Re: What is the ratio of OA to AC? (1) OD is half the length of DC [#permalink] New post   23 Sep 2018, 01:08
Expert Reply
I couldn't get you, We can still have angle ADC= 90, without O as Center.

PKN wrote:
I think we must consider point 'O' centre of the circle in the want we do consider Angle ADC 90 degree.

Posted from my mobile device
avatar
B
successpoint
Intern
Intern
Joined: 15 Jan 2018
Posts: 3
Own Kudos [?]: 0 [0]
Given Kudos: 13
Send PM
Re: What is the ratio of OA to AC? (1) OD is half the length of DC [#permalink] New post   23 Sep 2018, 01:32
gmatbusters wrote:
I couldn't get you, We can still have angle ADC= 90, without O as Center.

PKN wrote:
I think we must consider point 'O' centre of the circle in the want we do consider Angle ADC 90 degree.

Posted from my mobile device



We can't assume that OC is radius because it is not mentioned anywhere in the statement. The trap in DS problem is that if it is not given we can't assume.

If it's mentioned that OC is radius then the answer will be A .

Therefore it is E.
User avatar
D
PKN
Director
Director
Joined: 01 Oct 2017
Status:Learning stage
Posts: 827
Own Kudos [?]: 1300 [0]
Given Kudos: 41
WE:Supply Chain Management (Energy and Utilities)
Send PM
Re: What is the ratio of OA to AC? (1) OD is half the length of DC [#permalink] New post   23 Sep 2018, 02:10
gmatbusters wrote:
I couldn't get you, We can still have angle ADC= 90, without O as Center.

PKN wrote:
I think we must consider point 'O' centre of the circle in the want we do consider Angle ADC 90 degree.

Posted from my mobile device


My reasoning:-
1) Notice a square symbol at point D. And we say angle ADC or Angle ADO is 90 degree

In the same way,

2) Notice "a BOLD DOT mark" at point O. We can say point 'O' the centre of the circle.
User avatar
L
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 92945
Own Kudos [?]: 619197 [0]
Given Kudos: 81609
Send PM
CAT Tests Forum Quiz Mode
Re: What is the ratio of OA to AC? (1) OD is half the length of DC [#permalink] New post   23 Sep 2018, 03:22
Expert Reply
gmatbusters wrote:
Bunuel, Do we have to consider that O is Center?
if O is not the center, it seems E

Bunuel wrote:

What is the ratio of OA to AC?

(1) OD is half the length of DC
(2) The area of ADC is 20.


Show Spoiler
Attachment:
image008.jpg

___________________
Fixed. Thank you.
User avatar
bumpbot
Non-Human User
Joined: 09 Sep 2013
Posts: 32688
Own Kudos [?]: 822 [0]
Given Kudos: 0
Send PM
Re: What is the ratio of OA to AC? (1) OD is half the length of DC [#permalink] New post   03 Mar 2021, 05:30
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
GMAT Club Bot
gmatclubot
Re: What is the ratio of OA to AC? (1) OD is half the length of DC [#permalink]
03 Mar 2021, 05:30
Moderator:
Bunuel
Math Expert
92945 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions