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# In the figure above, what is the ratio KN/MN?

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Director
Joined: 07 Jun 2004
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In the figure above, what is the ratio KN/MN?  [#permalink]

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Updated on: 05 Jun 2015, 04:18
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In the figure above, what is the ratio KN/MN?

(1) The perimeter of rectangle KLMN is 30 meters.
(2) The three small rectangles have the same dimensions.

Attachment:

ds.jpg [ 13.75 KiB | Viewed 13093 times ]

Attachment:

2015-06-05_1517.png [ 3.84 KiB | Viewed 9991 times ]

Originally posted by rxs0005 on 12 Aug 2010, 14:42.
Last edited by Bunuel on 05 Jun 2015, 04:18, edited 2 times in total.
Edited the question and added the OA
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Posts: 53738
In the figure above, what is the ratio KN/MN?  [#permalink]

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12 Aug 2010, 15:07
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What is the ratio KN/MN?

(1) The perimeter of rectangle KLMN is 30 meters. Clearly insufficient as numerous combinations of sides will make a perimeter of 30.

(2) The 3 small rectangles have the same dimensions --> let the shorter sides of small rectangles be $$x$$ and longer side be $$y$$, so $$KN=LM=y$$ and $$MN=x+y$$. Also two smaller sides add up to bigger side, so $$x+x=2x=y$$ (LM, or KN, which is $$y$$ equal to the sum of 2 shorter sides). $$\frac{KN}{MN}=\frac{y}{x+y}=\frac{2x}{x+2x}=\frac{2}{3}$$. Sufficient.

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Director
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Re: In the figure above, what is the ratio KN/MN?  [#permalink]

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12 Aug 2010, 15:21
1
ah ... right ...

thank you i missed that part where

"Also two smaller sides add up to bigger side"
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Re: In the figure above, what is the ratio KN/MN?  [#permalink]

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05 Jun 2015, 11:33
Hi All,

This is a great 'pattern-matching' question, and you can TEST VALUES to prove that the pattern exists.

Since this is a DS question, we can't trust that the picture is drawn to scale. While it certainly appears that the 3 smaller rectangles are the same size, we don't know that for sure.

We're asked for the ratio of KN to MN...

Fact 1: The perimeter of rectangle KLMN is 30 meters.

This gives us the dimensions of the larger rectangle, but we don't know the dimensions of its 2 sides.

IF...
KN = 3 and MN = 10, then the answer to the question is 3/10

IF...
KN = 5 and MN = 16, then the answer to the question is 5/6
Fact 1 is INSUFFICIENT

Fact 2: The three small rectangles have the same dimensions.

Now THIS is an interesting piece of information. Since the small rectangles are all exactly the same, we can see that in each of those smaller rectangles....TWICE the SHORT side = LONG side

IF...
Long side = 2 and Short side = 1, then the answer to the question is 2/3

IF...
Long side = 4 and Short side = 2, then the answer to the question is 4/6 = 2/3

IF...
Long side = 3 and Short side = 1.5, then the answer to the question is 3/4.5 = 2/3

The answer is ALWAYS 2/3
Fact 2 is SUFFICIENT

GMAT assassins aren't born, they're made,
Rich
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# Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests Free Official GMAT Exam Packs + 70 Pt. Improvement Guarantee www.empowergmat.com/ *****Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***** Director Joined: 26 Oct 2016 Posts: 634 Location: United States Concentration: Marketing, International Business Schools: HBS '19 GMAT 1: 770 Q51 V44 GPA: 4 WE: Education (Education) Re: In the figure above, what is the ratio KN/MN? [#permalink] ### Show Tags 26 Jan 2017, 07:24 Statement (2) gives us a lot, including what we need to answer the question. 2) The three small rectangles have the same dimensions. First, we now know that all 3 shapes are rectangles. Second, we know that they're identical rectangles. Let's label all the short sides w and the long sides l. From the diagram, we can now see that 2w is the same as l (since LM = KN), so we know the relationship between w and l. So, let's go back to the original question: What's KN/MN? KN = l and MN = l + w Subbing in l = 2w, we get: KN = 2w and MN = 2w + w = 3w and KN/MN = 2w/3w = 2/3... sufficient. _________________ Thanks & Regards, Anaira Mitch Intern Joined: 06 May 2014 Posts: 44 In the figure above, what is the ratio KN/MN? [#permalink] ### Show Tags 12 Dec 2017, 09:59 EMPOWERgmatRichC wrote: Hi All, This is a great 'pattern-matching' question, and you can TEST VALUES to prove that the pattern exists. Since this is a DS question, we can't trust that the picture is drawn to scale. While it certainly appears that the 3 smaller rectangles are the same size, we don't know that for sure. We're asked for the ratio of KN to MN... Fact 1: The perimeter of rectangle KLMN is 30 meters. This gives us the dimensions of the larger rectangle, but we don't know the dimensions of its 2 sides. IF... KN = 3 and MN = 10, then the answer to the question is 3/10 IF... KN = 5 and MN = 16, then the answer to the question is 5/6 Fact 1 is INSUFFICIENT Fact 2: The three small rectangles have the same dimensions. Now THIS is an interesting piece of information. Since the small rectangles are all exactly the same, we can see that in each of those smaller rectangles....TWICE the SHORT side = LONG side IF... Long side = 2 and Short side = 1, then the answer to the question is 2/3 IF... Long side = 4 and Short side = 2, then the answer to the question is 4/6 = 2/3 IF... Long side = 3 and Short side = 1.5, then the answer to the question is 3/4.5 = 2/3 The answer is ALWAYS 2/3 Fact 2 is SUFFICIENT Final Answer: GMAT assassins aren't born, they're made, Rich Can you please explain why is it not working for : Long side= 1.5, short side =1. then the answer is 1.5/2.5=3/5 ? Am I missing something? _________________ Utilize your 'today' to build up your tomorrow'! .... Looking for some kudos here... EMPOWERgmat Instructor Status: GMAT Assassin/Co-Founder Affiliations: EMPOWERgmat Joined: 19 Dec 2014 Posts: 13765 Location: United States (CA) GMAT 1: 800 Q51 V49 GRE 1: Q170 V170 Re: In the figure above, what is the ratio KN/MN? [#permalink] ### Show Tags 12 Dec 2017, 11:22 Hi tanvi9, Based on the information in Fact 2 - the 3 small rectangles are IDENTICAL, so if you add 2 "short sides", the total equals 1 "long side." In your example, you set a 'short side' = 1 and a 'long side' = 1.5.... but that does NOT fit what we were told (1.5 is NOT equal to 1+1). IF.... you set the short side = 1, then the long side = 2 you set the long side = 1.5, then the short side = 0.75 With either of those examples, you'll end up with the same answer that I did (the answer to the question is still 2/3). GMAT assassins aren't born, they're made, Rich _________________ 760+: Learn What GMAT Assassins Do to Score at the Highest Levels Contact Rich at: Rich.C@empowergmat.com # Rich Cohen Co-Founder & GMAT Assassin Special Offer: Save$75 + GMAT Club Tests Free
Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/

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Joined: 06 May 2014
Posts: 44
Re: In the figure above, what is the ratio KN/MN?  [#permalink]

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12 Dec 2017, 11:44
Oh God that was stupid!

Thanks Rich!

EMPOWERgmatRichC wrote:
Hi tanvi9,

Based on the information in Fact 2 - the 3 small rectangles are IDENTICAL, so if you add 2 "short sides", the total equals 1 "long side." In your example, you set a 'short side' = 1 and a 'long side' = 1.5.... but that does NOT fit what we were told (1.5 is NOT equal to 1+1).

IF....
you set the short side = 1, then the long side = 2
you set the long side = 1.5, then the short side = 0.75

With either of those examples, you'll end up with the same answer that I did (the answer to the question is still 2/3).

GMAT assassins aren't born, they're made,
Rich

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Utilize your 'today' to build up your tomorrow'!

.... Looking for some kudos here...

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Re: In the figure above, what is the ratio KN/MN?  [#permalink]

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23 Dec 2018, 01:31
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Re: In the figure above, what is the ratio KN/MN?   [#permalink] 23 Dec 2018, 01:31
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# In the figure above, what is the ratio KN/MN?

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