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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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Difficulty:   55% (hard)

Question Stats: 59% (01:39) correct 41% (02:06) wrong based on 711 sessions

HideShow timer Statistics 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 15165 times ]

Attachment: 2015-06-05_1517.png [ 3.84 KiB | Viewed 12250 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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In the figure above, what is the ratio KN/MN?  [#permalink]

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

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2
ah ... right ...

thank you i missed that part where

"Also two smaller sides add up to bigger side"
EMPOWERgmat Instructor V
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GMAT 1: 800 Q51 V49 GRE 1: Q170 V170 Re: In the figure above, what is the ratio KN/MN?  [#permalink]

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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

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

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1
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.
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In the figure above, what is the ratio KN/MN?  [#permalink]

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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

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?
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GMAT 1: 800 Q51 V49 GRE 1: Q170 V170 Re: In the figure above, what is the ratio KN/MN?  [#permalink]

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

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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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_________________ Re: In the figure above, what is the ratio KN / MN   [#permalink] 06 Jun 2019, 06:05
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