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

 It is currently 06 May 2015, 21:29

### 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

# Gmat club test Quant 07 , Q18

Author Message
TAGS:
Intern
Joined: 30 Nov 2010
Posts: 48
Followers: 0

Kudos [?]: 6 [0], given: 27

Gmat club test Quant 07 , Q18 [#permalink]  11 Apr 2011, 17:27
00:00

Difficulty:

(N/A)

Question Stats:

56% (01:27) correct 44% (01:13) wrong based on 9 sessions
Hey guys another question which I think needs more opinions about:

If a lumberjack crew needs to secure a safety zone for cutting down the trees, how far from a given tree should the safety barrier be put up so that it is at least 5 meters away from the danger area, and the barrier perimeter is minimized? The first tree is the highest one.

1. The height of the first tree is 50m.
2. Currently the distance from the barrier to the top of the tree is 70 meters.

A) Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient
B) Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient
C) BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient
D) EACH statement ALONE is sufficient
E) Statements (1) and (2) TOGETHER are NOT sufficient
-------

So, should'nt the answer be "D" ?

From statement (1) , it is straight forward, it is sufficient.

From statement (2) alone we can say --> x^2 + (x + 5)^2 = 70^2 , and solve for x. (Pythagorus theorem).
** Please see the attached image of the triangle. **

AB = x = tree height.
BC = x+5 = distance of the barrier from base of the tree.
AC = 70 = the distance from the barrier to the top of the tree is 70 meters.

And hence, get x + 5 , which will give us ~=17.95. Hence statement (2) is sufficient.

Hence Ans=D.

Let me know if I getting something wrong here.

Thanks.
[Reveal] Spoiler: OA

Attachments

GMAT 07 - Q18.jpg [ 8.57 KiB | Viewed 1524 times ]

Intern
Joined: 30 Mar 2011
Posts: 8
Followers: 0

Kudos [?]: 1 [0], given: 4

Re: Gmat club test Quant 07 , Q18 [#permalink]  11 Apr 2011, 17:40
I think your solution with statement 2 assumes that the barrier is already exactly at the minimum safe distance, where it isn't indicated to be that way. So currently, the barrier could be anywhere.
Intern
Joined: 30 Nov 2010
Posts: 48
Followers: 0

Kudos [?]: 6 [0], given: 27

Re: Gmat club test Quant 07 , Q18 [#permalink]  11 Apr 2011, 17:44
The barrier is at "Radius of danger area" + 5(given in the problem).
"radius of danger area" = Height of the tree = x.

It's is known to be at (x + 5)m from the tree.
Manager
Joined: 05 Jul 2010
Posts: 204
Followers: 1

Kudos [?]: 12 [0], given: 18

Re: Gmat club test Quant 07 , Q18 [#permalink]  11 Apr 2011, 17:46
isn't in ST2 it doesn't tells whether it is the first tree or it is the highest one.
Intern
Joined: 30 Nov 2010
Posts: 48
Followers: 0

Kudos [?]: 6 [0], given: 27

Re: Gmat club test Quant 07 , Q18 [#permalink]  11 Apr 2011, 17:52
Quote:
Statement (1) by itself is sufficient. S1 tells us that the tree, if cut down, will hit the ground no farther than 50 meters away from its origin. Therefore, the barrier has to be at least 55 meters away.

Statement (2) by itself is insufficient. S2, without the height of the tree, is insufficient.

So, it says "height of the tree", which tree? Cannot we conclude that the answer speaks about height of the first tree?

I would agree with brandy96 if the answer said:

"Statement (2) by itself is insufficient. Since distance from the barrier to the top of *which* tree is unknown."
SVP
Joined: 16 Nov 2010
Posts: 1684
Location: United States (IN)
Concentration: Strategy, Technology
Followers: 31

Kudos [?]: 342 [0], given: 36

Re: Gmat club test Quant 07 , Q18 [#permalink]  11 Apr 2011, 22:01
Hmm.. Ambiguous wording.

fluke, Ian, please opine on this.
_________________

Formula of Life -> Achievement/Potential = k * Happiness (where k is a constant)

GMAT Club Premium Membership - big benefits and savings

Math Forum Moderator
Joined: 20 Dec 2010
Posts: 2035
Followers: 135

Kudos [?]: 1113 [0], given: 376

Re: Gmat club test Quant 07 , Q18 [#permalink]  12 Apr 2011, 00:17
subhashghosh wrote:
Hmm.. Ambiguous wording.

fluke, Ian, please opine on this.

I don't understand why the information about the first tree is so emphasized. Although there is indeed some part of the question that's not totally clear, I tend to agree with oster here.

The barrier is 70m away from THE given tree's top won't help us determine how far we should put our barrier . The tree could be a 2m tall tree whose base is $$\sqrt{(70)^2-2^2}$$ away from the barrier's base, in which case it is already secured but the perimeter needs to be minimized OR it could be a 65m tall tree whose base is $$\sqrt{(70)^2-(65)^2}$$ away from the barrier's base, in which case the barrier will need to be moved further. In both cases, the only information required is the height of the tree to decide how far the barrier should be.

Will wait for IanStewart's comment.
_________________
Manager
Joined: 03 Nov 2009
Posts: 65
Followers: 1

Kudos [?]: 10 [0], given: 17

Re: Gmat club test Quant 07 , Q18 [#permalink]  12 Apr 2011, 00:55
HI ,

I think the sentence - ''how far from a given tree should the safety barrier be put up so that it is at least 5 meters away from the danger area''

and the Option 2 - ''Currently the distance from the barrier to the top of the tree is 70 meters''

Make it clear that the current distance is not the right distance and so the hypotenuse of 70 Mts is not that of the triangle whose base would be the actual barrier length that needs to be set.

Hence Ans - C.
GMAT Instructor
Joined: 24 Jun 2008
Posts: 978
Location: Toronto
Followers: 281

Kudos [?]: 799 [1] , given: 3

Re: Gmat club test Quant 07 , Q18 [#permalink]  12 Apr 2011, 11:39
1
KUDOS
chethanjs wrote:
If a lumberjack crew needs to secure a safety zone for cutting down the trees, how far from a given tree should the safety barrier be put up so that it is at least 5 meters away from the danger area, and the barrier perimeter is minimized? The first tree is the highest one.

1. The height of the first tree is 50m.
2. Currently the distance from the barrier to the top of the tree is 70 meters.

I received a PM asking for comment. This is one of those questions that tests whether you can guess what the question designer was thinking, rather than testing any mathematical ability. I frankly have no idea what the question means, and if I list the problems with the question, it's a pretty long list:

* GMAT test takers aren't, by and large, lumberjacks, so the question needs to define what it means by 'safety zone' and 'danger area'.

* The question talks first about a 'given tree' and then about a 'first tree'; are these the same tree? That's not clear, and it's crucially important.

* If I have a group of trees, there is no particular tree which I could logically call the 'first' tree. Trees aren't in some kind of sequence.

* The question talks about the 'perimeter' of the barrier. This suggests that the barrier is some kind of polygon (if it were a circle, the question should discuss its 'circumference'). It's then not altogether clear what's meant when the question asks 'how far' the polygonal barrier should be from the circular(?) 'danger area'; we're not measuring the distance between points but rather between shapes.

* The solution seems to assume that only the tallest tree matters. But if I have three trees in a line, where T is the tallest tree and measures 50 meters in height, and A and B both measure 40 meters in height:

---A-----T-----B-----

and I erect a barrier enclosing these trees, then if A and B are far enough from T, then they are certainly relevant here: I need to position my barrier 45 meters from A and B to ensure I have 5 meters of leeway as the question requires. It's only if you assume that by 'first tree' they mean 'tree closest to the barrier' that you can ignore the other trees.

* Statement 2 says that "Currently the distance from the barrier to the top of the tree is 70 meters" whereas the stem asks where the barrier should be 'put up'. Statement 2 suggests that the barrier has already been put up. That makes no sense.

It's rare that I read a question and simply have no understanding of what it's asking, but that's the case here. It's pretty much pointless to attempt to answer it, since you'd really need to have some psychic ability to work out what the question designer intended.
_________________

Nov 2011: After years of development, I am now making my advanced Quant books and high-level problem sets available for sale. Contact me at ianstewartgmat at gmail.com for details.

Private GMAT Tutor based in Toronto

Intern
Joined: 30 Nov 2010
Posts: 48
Followers: 0

Kudos [?]: 6 [0], given: 27

Re: Gmat club test Quant 07 , Q18 [#permalink]  12 Apr 2011, 11:50
Haha...damn. I paid 79 bucks for these GMAT club , I hope they worth atleast half those bucks. Just started working on them....

Posted from my mobile device
Math Forum Moderator
Joined: 20 Dec 2010
Posts: 2035
Followers: 135

Kudos [?]: 1113 [0], given: 376

Re: Gmat club test Quant 07 , Q18 [#permalink]  12 Apr 2011, 11:58
IanStewart wrote:
chethanjs wrote:
If a lumberjack crew needs to secure a safety zone for cutting down the trees, how far from a given tree should the safety barrier be put up so that it is at least 5 meters away from the danger area, and the barrier perimeter is minimized? The first tree is the highest one.

1. The height of the first tree is 50m.
2. Currently the distance from the barrier to the top of the tree is 70 meters.

I received a PM asking for comment. This is one of those questions that tests whether you can guess what the question designer was thinking, rather than testing any mathematical ability. I frankly have no idea what the question means, and if I list the problems with the question, it's a pretty long list:

* GMAT test takers aren't, by and large, lumberjacks, so the question needs to define what it means by 'safety zone' and 'danger area'.

* The question talks first about a 'given tree' and then about a 'first tree'; are these the same tree? That's not clear, and it's crucially important.

* If I have a group of trees, there is no particular tree which I could logically call the 'first' tree. Trees aren't in some kind of sequence.

* The question talks about the 'perimeter' of the barrier. This suggests that the barrier is some kind of polygon (if it were a circle, the question should discuss its 'circumference'). It's then not altogether clear what's meant when the question asks 'how far' the polygonal barrier should be from the circular(?) 'danger area'; we're not measuring the distance between points but rather between shapes.

* The solution seems to assume that only the tallest tree matters. But if I have three trees in a line, where T is the tallest tree and measures 50 meters in height, and A and B both measure 40 meters in height:

---A-----T-----B-----

and I erect a barrier enclosing these trees, then if A and B are far enough from T, then they are certainly relevant here: I need to position my barrier 45 meters from A and B to ensure I have 5 meters of leeway as the question requires. It's only if you assume that by 'first tree' they mean 'tree closest to the barrier' that you can ignore the other trees.

* Statement 2 says that "Currently the distance from the barrier to the top of the tree is 70 meters" whereas the stem asks where the barrier should be 'put up'. Statement 2 suggests that the barrier has already been put up. That makes no sense.

It's rare that I read a question and simply have no understanding of what it's asking, but that's the case here. It's pretty much pointless to attempt to answer it, since you'd really need to have some psychic ability to work out what the question designer intended.

_________________
Intern
Joined: 30 Nov 2010
Posts: 48
Followers: 0

Kudos [?]: 6 [0], given: 27

Re: Gmat club test Quant 07 , Q18 [#permalink]  12 Apr 2011, 17:40
I think the Club tests should be revised by the author(s). Just saying.
SVP
Joined: 16 Nov 2010
Posts: 1684
Location: United States (IN)
Concentration: Strategy, Technology
Followers: 31

Kudos [?]: 342 [0], given: 36

Re: Gmat club test Quant 07 , Q18 [#permalink]  12 Apr 2011, 18:25
I think I would ignore this question when I write the test m07.
_________________

Formula of Life -> Achievement/Potential = k * Happiness (where k is a constant)

GMAT Club Premium Membership - big benefits and savings

Re: Gmat club test Quant 07 , Q18   [#permalink] 12 Apr 2011, 18:25
Similar topics Replies Last post
Similar
Topics:
1 GMAT Club Quant Test 1 23 Mar 2013, 14:20
1 Gmat Club Quant test 3 19 Nov 2012, 02:49
1 M07-11 - GMAT club test 3 11 Sep 2012, 18:48
GMAT CLub Tests Quants 1 11 May 2009, 04:51
1 m07q18 16 23 Jul 2008, 04:58
Display posts from previous: Sort by