New questions posted on the CR forum and SC forum. Answer + Explanation = Kudos

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 Your Progress

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 350,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

A square wooden plaque has a square brass inlay in the center, leaving a wooden strip of uniform width around the brass square. If the ratio of the brass area to the wooden area is 25 to 39, which of the following could be the width, in inches, of the wooden strip?

I. 1 II. 3 III. 4

(A) I only (B) II only (C) I and II only (D) I and III only (E) I, II , and III

Problem Solving Question: 175 Category:Geometry Area Page: 85 Difficulty: 600

Each week we'll be posting several questions from The Official Guide For GMAT® Quantitative Review, 2ND Edition and then after couple of days we'll provide Official Answer (OA) to them along with a slution.

We'll be glad if you participate in development of this project: 1. Please provide your solutions to the questions; 2. Please vote for the best solutions by pressing Kudos button; 3. Please vote for the questions themselves by pressing Kudos button; 4. Please share your views on difficulty level of the questions, so that we have most precise evaluation.

Re: hard problem OG Quant 2nd edition [#permalink]
15 Jan 2010, 03:26

9

This post received KUDOS

Expert's post

1

This post was BOOKMARKED

hrish88 wrote:

A square wooden plaque has a square brass inlay in the center ,leaving a wooden strip of uniform width around the brass square.if the ratio of the brass area to the wooden area is 25 to 39,which of the following could be the width ,in inches ,of the wooden strip.

I. 1 II. 3 III. 4

A.I only B.II only C.III only D.I and III only e.I,II and III

We are asked which value of \frac{y-x}{2} is possible. \frac{y-\frac{5}{8}y}{2}=\frac{3}{16}y=?.

Well, expression \frac{3}{16}y can take ANY value depending on y: 1, 3, 4, 444, 67556, 0,9, ... ANY. Basically we are given the ratios of the sides (5/8), half of their difference can be any value we choose, there won't be any "impossible" values at all.

Re: hard problem OG Quant 2nd edition [#permalink]
15 Jan 2010, 08:49

let the width of the wooden part = w let the width of the brass part = b given brass area/wooden area = 25/39 area of brass part = b^2 area of wooden part = (b+2w)^2 - b^2 Simplifying 64b^2=25(b+2w)^2 8b=5b+10w b=10w/3

b has to be an integer or a terminating decimal. We can't have a width of 10/3 in real life (note the question doesn't ask for approximate width.) hence w has to be a multiple of 3. Answer is B. _________________

A square wooden plaque has a square brass inlay in the [#permalink]
15 Jan 2010, 09:44

4

This post received KUDOS

Expert's post

atish wrote:

let the width of the wooden part = w let the width of the brass part = b given brass area/wooden area = 25/39 area of brass part = b^2 area of wooden part = (b+2w)^2 - b^2 Simplifying 64b^2=25(b+2w)^2 8b=5b+10w b=10w/3

b has to be an integer or a terminating decimal. We can't have a width of 10/3 in real life (note the question doesn't ask for approximate width.) hence w has to be a multiple of 3. Answer is B.

Are you saying that in real life everything has the integer or terminating decimal length? Why cannot we have repeated decimal or even irrational number as width of something?

Take the square with side 1, diagonal would be \sqrt{2}, it's not an integer or terminating decimal.

Also it's possible to divide the line segment into three equal parts, Google it and you find that it's quite easy. _________________

Re: hard problem OG Quant 2nd edition [#permalink]
15 Jan 2010, 10:25

Quote:

Are you saying that in real life everything has the integer or terminating decimal length? Why can not we have repeated decimal or even irrational number as width of something?

Take the square with side 1, diagonal would be \sqrt{2}, it's not an integer or terminating decimal.

Also it's possible to divide the line segment into three equal parts, google it and you find that it's quite easy.

That takes the question to a whole new dimension, I do understand what you are saying though. If the width of something is 10/3 that means you can never (accurately) measure it. The width of the brass square can never be measured practically, it can be only measured mathematically. If such a square was to be made, the creator would have to take a square of 10/10 dimension, divide it into 9 exactly equal parts and use one of them, he/she could never make just the square as it would be impossible to measure 10/3 inches. I do get the concept, but don't like the fact that a question can be based on it. _________________

Re: hard problem OG Quant 2nd edition [#permalink]
15 Jan 2010, 12:09

Bunuel wrote:

Basically we are given the ratios of the sides (5/8), half of their difference can be any value we choose, there won't be any "impossible" values at all.

Hope it's clear.

Wow such a simple concept i must have left my brain someplace else.

Re: hard problem OG Quant 2nd edition [#permalink]
24 Mar 2010, 05:10

3

This post received KUDOS

hrish88 wrote:

A square wooden plaque has a square brass inlay in the center ,leaving a wooden strip of uniform width around the brass square.if the ratio of the brass area to the wooden area is 25 to 39,which of the following could be the width ,in inches ,of the wooden strip.

I. 1 II. 3 III. 4

A.I only B.II only C.III only D.I and III only e.I,II and III

Area of brass square/ area of wooden strip = 25 /39 lets say length of the wooden plaque= l and length of the square brass = x then x^2 / (l^2 - x^2) = 25/39 =>39x^2 = 25l^2 - 25x^2 =>64x^2 = 25l^2 =>8x = 5l Width of wooden strip should be l-x =>x = 5l/8 so l -x = l = 5l/8 = 3l/8

Now 3l/8 could be any value depending on the value of l so answer is E. _________________

We are asked which value of \frac{y-x}{2} is possible. \frac{y-\frac{5}{8}y}{2}=\frac{3}{16}y=?.

Well, expression \frac{3}{16}y can take ANY value depending on y: 1, 3, 4, 444, 67556, 0,9, ... ANY. Basically we are given the ratios of the sides (5/8), half of their difference can be any value we choose, there won't be any "impossible" values at all.

Hope it's clear.

To generalize then, since the answer does not seem to depend on the fact that the ration is 25/39, can it be said that regardless of what the ratio is, the width of strip can be ANYTHING? _________________

We are asked which value of \frac{y-x}{2} is possible. \frac{y-\frac{5}{8}y}{2}=\frac{3}{16}y=?.

Well, expression \frac{3}{16}y can take ANY value depending on y: 1, 3, 4, 444, 67556, 0,9, ... ANY. Basically we are given the ratios of the sides (5/8), half of their difference can be any value we choose, there won't be any "impossible" values at all.

Hope it's clear.

To generalize then, since the answer does not seem to depend on the fact that the ration is 25/39, can it be said that regardless of what the ratio is, the width of strip can be ANYTHING?

Yes, width can have any positive value: the larger the width is the larger the whole square would be. _________________

Re: hard problem OG Quant 2nd edition [#permalink]
19 Sep 2010, 14:41

I actually created equation and substituted width value to conclude E. I should have simply thought straight like Bunuel and marked E in 15 sec. _________________

If you like my post, consider giving me some KUDOS !!!!! Like you I need them

Re: hard problem OG Quant 2nd edition [#permalink]
17 Jan 2011, 11:50

Bunuel wrote:

hrish88 wrote:

A square wooden plaque has a square brass inlay in the center ,leaving a wooden strip of uniform width around the brass square.if the ratio of the brass area to the wooden area is 25 to 39,which of the following could be the width ,in inches ,of the wooden strip.

I. 1 II. 3 III. 4

A.I only B.II only C.III only D.I and III only e.I,II and III

Why would ANY width of the strip be impossible?

Answer: E.

That was my rationale exactly. I got the answer correct, but the explanation in the book made me feel like I did not grasp the underlying math. Thanks Bunuel.

Re: A square wooden plaque has a square brass inlay in the [#permalink]
01 Apr 2012, 07:43

1

This post received KUDOS

Expert's post

mymbadreamz wrote:

I didn't understand the statement "We are asked which value of (y-x)/2 is possible" . Can someone explain?

Question asks about the possible width, in inches, of the wooden strip.

Let the the side of small square be x and the big square y, then the width of the wooden strip would be \frac{y-x}{2}, which means that we are asked to determine the possible values of this exact expression.

Re: hard problem OG Quant 2nd edition [#permalink]
01 Sep 2012, 06:48

Bunuel wrote:

hrish88 wrote:

A square wooden plaque has a square brass inlay in the center ,leaving a wooden strip of uniform width around the brass square.if the ratio of the brass area to the wooden area is 25 to 39,which of the following could be the width ,in inches ,of the wooden strip.

I. 1 II. 3 III. 4

A.I only B.II only C.III only D.I and III only e.I,II and III

Why would ANY width of the strip be impossible?

Answer: E.

Hi Bunuel, this was the most appropriate reason for the answer; however, can there be a case where such a condition("any possible width of the strip") might fail, provided there is no restriction on dimensions to be integral or non integral? _________________

Whatever one does in life is a repetition of what one has done several times in one's life! If my post was worth it, then i deserve kudos

Re: A square wooden plaque has a square brass inlay in the [#permalink]
18 Sep 2012, 10:50

Bunuel wrote:

mymbadreamz wrote:

Why is it not y-x? Why do we calculate (y-x)/2?

Consider the diagram below:

Attachment:

Wooden strip.png

As you can see the width of the wooden strip (the width of grey strip) is \frac{y-x}{2}.

total length is 8x and the length of the countertop is 5x.so the one side length of the untiled area is w = 8x-5x/2 =3x/2 .Since x could be any value so the answer is E..Am I right Bunuel ?

gmatclubot

Re: A square wooden plaque has a square brass inlay in the
[#permalink]
18 Sep 2012, 10:50

Wow...I'm still reeling from my HBS admit . Thank you once again to everyone who has helped me through this process. Every year, USNews releases their rankings of...

Almost half of MBA is finally coming to an end. I still have the intensive Capstone remaining which started this week, but things have been ok so far...