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# m9 q34

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Manager
Joined: 14 Jun 2008
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18 Jul 2008, 02:44
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$$A$$ , $$B$$ , and $$C$$ are points on the plane. Is $$AB \lt 10$$ ?

1. $$AC + BC = 10$$
2. $$AB + AC \gt 10$$

Source: GMAT Club Tests - hardest GMAT questions

REVISED VERSION OF THIS QUESTION IS HERE: m9-q34-70894-20.html#p1120622
Senior Manager
Joined: 07 Jan 2008
Posts: 399
Re: m9 q34 [#permalink]

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18 Jul 2008, 04:29
A.
Sum of two sides of triangle is always greater than the rest.
Manager
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Re: m9 q34 [#permalink]

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18 Jul 2008, 04:52
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but how do u know its a triangle?
and not on a straight line?
Manager
Joined: 15 Jul 2008
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Re: m9 q34 [#permalink]

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18 Jul 2008, 05:39
IMO the answer is E. Neither equation nor the inequality tells u if the 3 points are collinear or vertices of triangle. So nothing can be inferrd.
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Re: m9 q34 [#permalink]

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18 Jul 2008, 08:19
1
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I am thinking E.

I agree, neither by itself gives you enough information. We're really only discussing C or E.

So, if you take the two statements and you make them AC + BC = AB + AC ( and I realize #2 is >, not =, but follow me for a second), you get
AC + BC = AB + AC The AC on each side cancels out, so you have BC = AB. Because AB + AC is actually Greater than, since AC is the same, the difference must be in AB, which must be larger than BC, but we don't know how much larger.

We know AC is less than 10 because AC + BC = 10. A number + another number will always be less than the sum of the two numbers (as long as they're both positive).

AC can be anything up to (but not including) 10. It could be 9.9999999999999999999, and BC = 10 minus that (i'm not counting the 9's).

Because AB + AC > 10, AB + AC = 300 or AB + AC = 10.1. The point is we just don't know and together they're insufficient.

sset009 wrote:
$$A$$ , $$B$$ , and $$C$$ are points on the plane. Is $$AB \lt 10$$ ?

1. $$AC + BC = 10$$
2. $$AB + AC \gt 10$$

(C) 2008 GMAT Club - m09#34

* Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient
* Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient
* BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient
* EACH statement ALONE is sufficient
* Statements (1) and (2) TOGETHER are NOT sufficient

Couldnt understand the official explanation

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J Allen Morris
**I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$. GMAT Club Premium Membership - big benefits and savings Current Student Joined: 28 Dec 2004 Posts: 3357 Location: New York City Schools: Wharton'11 HBS'12 Re: m9 q34 [#permalink] ### Show Tags 18 Jul 2008, 08:33 i have fallen for such mistakes before..now its etched into memory.. you dont know if the points are in a triangular coordinates.. E is best.. Intern Joined: 10 Sep 2008 Posts: 36 M09 #34 [#permalink] ### Show Tags 29 Sep 2008, 17:25 A ,B , and C and are points on the plane. Is AB<10 ? 1) AC+BC=10 2) AB+AC >10 Answer: E Can someone pls explain this DS answer to me ? Do we assume that is a triangle? Maybe it is a straight line? If it is a triangle, then S1 is sufficient because the other side needs to less than ten. Thank you VP Joined: 18 May 2008 Posts: 1261 M09,#34 [#permalink] ### Show Tags 18 Mar 2009, 03:49 A, B , and C are points on the plane. Is AB<10 ? 1. AC+BC=10 2. AB+AC>10 Shldnt 1 be sufficient ? bcos if we make a triangle of these three points then triangle property says "The sum of the lengths of any two sides of a triangle must be greater than the third side" then AC+BC>AB since AB+BC=10 Hence AB<10 SVP Joined: 30 Apr 2008 Posts: 1874 Location: Oklahoma City Schools: Hard Knocks Re: M09,#34 [#permalink] ### Show Tags 18 Mar 2009, 05:01 You're right if you think of it as a triangle, but a triangle is not the only option. The points are on a plane, and the points COULD be in a line and still on the same plane. If this happens, and say the points go A-C-B, then the distance between AB would be 10, not less than 10, so 1 is insufficient. ritula wrote: A, B , and C are points on the plane. Is AB<10 ? 1. AC+BC=10 2. AB+AC>10 Shldnt 1 be sufficient ? bcos if we make a triangle of these three points then triangle property says "The sum of the lengths of any two sides of a triangle must be greater than the third side" then AC+BC>AB since AB+BC=10 Hence AB<10 _________________ ------------------------------------ J Allen Morris **I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$.

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VP
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18 Mar 2009, 09:11
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oh yes....i didnt think of dat option. thanks!
jallenmorris wrote:
You're right if you think of it as a triangle, but a triangle is not the only option. The points are on a plane, and the points COULD be in a line and still on the same plane. If this happens, and say the points go A-C-B, then the distance between AB would be 10, not less than 10, so 1 is insufficient.

ritula wrote:
A, B , and C are points on the plane. Is AB<10 ?

1. AC+BC=10
2. AB+AC>10

Shldnt 1 be sufficient ?
bcos if we make a triangle of these three points then triangle property says "The sum of the lengths of any two sides of a triangle must be greater than the third side" then AC+BC>AB
since AB+BC=10 Hence AB<10
Senior Manager
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Re: M09 #34 [#permalink]

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30 Jul 2009, 08:57
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This question is so tricky! Gmat test takers can't be THAT cunning that can they!?
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Re: M09 #34 [#permalink]

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31 Jul 2010, 13:05
Interesting. I assume that if the question prompt was something like "A, B and C are distinct points on a plane" that the answer would be (a)?
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Re: m9 q34 [#permalink]

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06 Sep 2010, 22:24
IMO E we can conclude S1 is suff. if it was given that points are not in line
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Manager
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Re: m9 q34 [#permalink]

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11 Sep 2010, 07:35
At first glance, I also picked up A as an answer. Though, the trick here is to understand the fine difference between a line and plane and related peculiarities of both. I must remember it now! Thanks for posting such a nice question.
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Manager
Joined: 25 Jul 2010
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Re: m9 q34 [#permalink]

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16 Oct 2010, 05:40
Just wanted to be sure :
If it was specified that A,B and C are distinct points in a plane, would answer A be sufficient?

Also, if mentioned that A,B and C forms a triangle, I am sure answer A is sufficient.

Please correct me if I am wrong in my understanding.
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Re: m9 q34 [#permalink]

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09 Sep 2011, 05:52
hmm, my way of thinking is below-

stm 1 -no info about AB
stm 2- insuf info

mix of stm 1 and stm 2-
AC + BC = 10 let AC equal 9 (max possible value)
then AB + AC> 10 AB +9>10 AB >1 (it could be 5 or 15,so insuf )

AC + BC = 10 let AC equal 1 (min possible value)
then AB + AC> 10 AB +1>10 AB >9 (it could be 10 or 15 ,so insuf)

answ is E
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Re: m9 q34 [#permalink]

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09 Sep 2011, 06:37
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Yes answer should be E. Here is my explanation -

Stmt1: AC+BC = 10
Try to plot three points on a sheet of paper.You can either have a triangle or a line.
- If you plot a triangle, it is clear that AB<10 (sum of any two sides will always be more than the third side).
- If you plot a line using three points, and given that AC+BC = 10, we can conclude that C lies between A and B on the line. In other words, AC+BC=AB=10.
So, in one case you get AB<10 and in other case you get AB=10. Thus INSUFFICIENT.

Stmt2: AB+AC > 10 (10.1 or 20, it doesnt matter. Both are greater than 10)
1+10 > 10 (AB=1, and is thus <10)
10+10 > 10 (AB=10 and is equal to 10)
2 values, thus INSUFFICIENT.

Lets combine the two statements now.

From stmt1, we have AC=10-BC. Put this is stmt2. That is AB + 10 - BC >10.
We also know from stmt1 that AB can be either <10 or =10. You can now put AB=10 and AB=9 in equation above to see that both can be valid. Thus together the two statements are INSUFFICIENT. Hence, E.

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Re: m9 q34 [#permalink]

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09 Sep 2011, 06:53
My initial response was A based on properties of triangles. Then E because the points could be a straight line. Duh! Tricky GMAT, tricky!
Manager
Joined: 11 Feb 2011
Posts: 75
Re: m9 q34 [#permalink]

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09 Sep 2011, 16:15
tough question..but can't figure out whether points can form a triangle or colinear & even it didn't say whether all points are distinct. answer is E
Intern
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Re: m9 q34 [#permalink]

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11 Sep 2011, 07:13
Let the three points be anywhere. Since it is not mentioned that it is a triangle therefore we cannot use only Statement 1
using Statement 1 and 2
AB > AC
and AB > 10 -BC
the second is more interesting as we can start by having A,B and C in a straight line and as we move point B (or C, or A) we get various values of a triangle with values like
AB > 10, AB>9 AB>8... so forth which makes both statements not sufficient
Re: m9 q34   [#permalink] 11 Sep 2011, 07:13

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# m9 q34

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