OG-12 DS #117

This topic has expert replies
User avatar
Community Manager
Posts: 1537
Joined: Mon Aug 10, 2009 6:10 pm
Thanked: 653 times
Followed by:252 members

OG-12 DS #117

by papgust » Sat Mar 06, 2010 7:41 pm
In the figure above, points A, B, C, D, and E lie on a line. A is on both circles, B is the center of the smaller circle, C is the center of the larger circle, D is on the smaller circle, and E is on the larger circle. What is the area of the region inside the larger circle and outside the smaller circle?

(1) AB = 3 and BC = 2
(2) CD = 1 and DE = 4

Please refer the diagram in OG

OA: D


My doubt:

I actually selected A and ignored statement (ii) as insufficient because I thought that i should not trust the diagram without further information. In other words, statement (ii) says that CD=1 and DE=4. From the diagram, we could infer that CE is the radius and therefore CE = CD+DE = 1+4 = 5 (This is what is given in OG-12)

But, i thought that D could be outside the inner circle and could also be inside the inner circle. That is, there could be 2 possibilities

If D is outside the inner circle, then CE = CD+DE = 5 (radius of outer circle)
If D is inside the inner circle, then CE = DE - CD = 3 (radius of outer circle)

For this reason, i ignored B and selected A.

What is wrong in my thought? Did i go beyond the scope of ambiguity in diagrams? If so, why?
Source: — Data Sufficiency |

User avatar
Master | Next Rank: 500 Posts
Posts: 142
Joined: Sat Feb 20, 2010 7:23 pm
Thanked: 8 times
Followed by:1 members

by bpgen » Sun Mar 07, 2010 1:09 am
As it's saying 'D is on the smaller circle, and E is on the larger circle" , that means D, E are laying on circumference of circle... not inside or outside. Hope this helps.
"Ambition is the path to success. Persistence is the vehicle you arrive in."

User avatar
Community Manager
Posts: 1537
Joined: Mon Aug 10, 2009 6:10 pm
Thanked: 653 times
Followed by:252 members

by papgust » Sun Mar 07, 2010 4:47 am
Alright. But, C could be either inside or outside the smaller circle. Is there any proof provided in the question stem that C is only inside the smaller circle?

User avatar
Master | Next Rank: 500 Posts
Posts: 142
Joined: Sat Feb 20, 2010 7:23 pm
Thanked: 8 times
Followed by:1 members

by bpgen » Sun Mar 07, 2010 6:53 am
What does it mean? If you see diagram it could be seen clearly... :-)

Anyway, would that position of C, affecting your decision making process?
Even for your sake, I could assume C is outside of small circle, still we could solve this problem..

(1) AB = 3 and BC = 2
(2) CD = 1 and DE = 4

so if C is inside, no issues, solution is in OG,
Let's see C is outside of small circle,
So, big circle's radius would be DE-CD, where small circle's diameter would be 2(DE-CD)-DE, i.e AD
Hope this helps.
"Ambition is the path to success. Persistence is the vehicle you arrive in."

User avatar
Community Manager
Posts: 1537
Joined: Mon Aug 10, 2009 6:10 pm
Thanked: 653 times
Followed by:252 members

by papgust » Sun Mar 07, 2010 9:01 am
bpgen wrote:What does it mean? If you see diagram it could be seen clearly... :-)
My question is just this. It can be seen clearly from the diagram that C is inside the inner circle. Agreed. But the diagram is not measured to scale. Neither it is mentioned specifically that C falls within the inner circle.

So, to what extent i could trust the diagram?

Really appreciate you for being patient to answer my questions :)

Legendary Member
Posts: 610
Joined: Fri Jan 15, 2010 12:33 am
Thanked: 47 times
Followed by:2 members

by kstv » Sun Mar 07, 2010 10:21 am
It is like the Emperors cloth , everyone can see it but I cannot see the diagram.

User avatar
Master | Next Rank: 500 Posts
Posts: 142
Joined: Sat Feb 20, 2010 7:23 pm
Thanked: 8 times
Followed by:1 members

by bpgen » Sun Mar 07, 2010 11:06 am
kstv, pls refer to OG-12 DS #117
"Ambition is the path to success. Persistence is the vehicle you arrive in."