It is currently 25 Jun 2017, 03:47

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Geometry

Author Message
Manager
Joined: 21 Feb 2009
Posts: 106

### Show Tags

26 Mar 2009, 16:17
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

### HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

DS in Geometry
Attachments

DegreeMeasure.jpg [ 34.66 KiB | Viewed 1707 times ]

Manager
Joined: 05 Jan 2009
Posts: 81

### Show Tags

26 Mar 2009, 18:19
ANS:D
recently discussed in forum.
Manager
Joined: 21 Feb 2009
Posts: 106

### Show Tags

27 Mar 2009, 14:47
Can you please post the link which has the explanation,Probably last time i missed it.
Senior Manager
Joined: 30 Nov 2008
Posts: 489
Schools: Fuqua

### Show Tags

27 Mar 2009, 15:42
IMO D.

I tired solving this problem using one of the basic rules of the triable.

Exterior angle of a triable = sum of the opposite interior angles.

It is given AB = OC.

Following can also be derived. OB = AB.
Let <BAO = <BOA = x (Because of the Isoceles triable proerty)
Let <BCO = <CBO = y. (Becuase of the isoceles triangle property)

From stmt1 : <COD = 60 Then x + y = 60 (By the rule, stated above)
Again <BAO + <BOA = <CBO ==> y + y = x ==> 2y = x(By the rule stated above)

Solving these two, we can get the value of y. Hence sufficient.

From Stmt 2: Given <BCO = 40. ==> < CBO = 40.

Again, <BAO + <BOA = <CBO ==> y + y = x ==> 2y = x(By the rule stated above)
Here we know x = 40.

Solving it, we can get the value of Y. Hence sufficient.

Other solutions can be found in the following link.

gmatprep-2-triangle-semicircle-76801.html
Manager
Joined: 28 Jul 2004
Posts: 136
Location: Melbourne
Schools: Yale SOM, Tuck, Ross, IESE, HEC, Johnson, Booth

### Show Tags

27 Mar 2009, 15:43
nitindas wrote:
Can you please post the link which has the explanation,Probably last time i missed it.

Don't know the post but, here is the solution:

from the stem , AB = OC = OB (Since OC and OB are radii of the same circle) --- (a)

from (1) , we have <COD = 60 . Let's solve:

Consider triangle CBO.
<CBO + <COB + <BCO = 180 (sum of angles in a triangle) --- (b)
<CBO = <BCO (since OB = OC, its an isosceles triangle)

equation "b" becomes:
2<CBO + <COB = 180
Now, <CBO = <BAO + <BOA (external angle in a triangle is equal to the sum of two internal angles)
also, <BAO = <BOA (from equation a above)

which implies, 4<BAO + <COB = 180 --> 4<BAO + (120 - <BOA) = 180

or, 4<BAO = 120 - <BOA = 180
or, 3<BAO = 60 (since <BAO = <BOA )
or, <BAO = 20

Hence (1) is sufficient.

Now from (2) we have, <BCO = 40 --> <CBO = 40 --> 2<BAO = 40 --> <BAO = 20. Hence (2) is sufficient.

I have not explained here but if you understood (1) above, I think this is easy to stand.

_________________

kris

Re: Geometry   [#permalink] 27 Mar 2009, 15:43
Display posts from previous: Sort by