Author 
Message 
TAGS:

Hide Tags

Manager
Joined: 18 Jun 2007
Posts: 67

The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
19 Jul 2008, 20:29
6
This post received KUDOS
24
This post was BOOKMARKED
Question Stats:
62% (00:40) correct 38% (00:55) wrong based on 437 sessions
HideShow timer Statistics
The cost of a square slab is proportional to its thickness and also proportional to the square of its length. What is the cost of a square slab that is 3 meters long and 0.1 meter thick? (1) The cost of a square slab that is 2 meters long and 0.2 meter thick is $160 more than the cost of a square slab that is 2 meters long and 0.1 meter thick. (2) The cost of a square slab that is 3 meters long and 0.1 meter thick is $200 more than the cost of a square slab that is 2 meters long and 0.1 meter thick. Attachment:
DS.jpg [ 91.34 KiB  Viewed 212 times ]
Official Answer and Stats are available only to registered users. Register/ Login.
Last edited by Bunuel on 06 Feb 2018, 20:09, edited 1 time in total.
Renamed the topic and edited the question.



Director
Joined: 10 Sep 2007
Posts: 934

Re: The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
19 Jul 2008, 20:47
5
This post received KUDOS
7
This post was BOOKMARKED
As per questions c = ktl^2 where c is the cost, t is the thickness, l is the length and k is coefficient of proportionality.
1) k*0.2*4  k*0.1*4 = 160. This will give us k = 400 Answer to question c = 400*0.1*9 = 360
2) k*0.1*9  k*0.1*4 = 200. This will give us k = 400 Answer to question c = 400*0.1*9 = 360
Both option answers the question, so D.



Manager
Joined: 18 Jun 2007
Posts: 67

Re: The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
19 Jul 2008, 20:55
2
This post was BOOKMARKED
I read this question wrong. I was thinking that the cost was different for the length vs the thickness..... thx..



Senior Manager
Joined: 23 May 2006
Posts: 322

Re: The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
19 Jul 2008, 20:56
1
This post received KUDOS
The cost of a square slab is proportional to its thickness and also proportional to the square of its length. What is the cost of a square slab that is 3 meters long and 0.1m thick.
(1) The cost of a square slab that is 2m long and 0.2 m thick is $160 more than the cost of a slab that is 2m long and 0.1 m thick area1 = 2x2x0.2 = 0.4m^2; area2 = 2x2x0.1 = 0.2m^2 A1  A2 = 0.2m^2 = $160; so you can calculate the area of 0.1m^2 and you know that the are of the salb in question is 3x3x.1 = 0.9m^2
(2) The cost of a square slab that is 3 m long and 0.1 m thick is 200 more than the cost of a square slab that is 2m long and 0.1 m thick Follow same logic as S1.
Ans: D



VP
Joined: 16 Jul 2009
Posts: 1476
Schools: CBS
WE 1: 4 years (Consulting)

Re: The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
07 Sep 2009, 11:50
1
This post received KUDOS
1
This post was BOOKMARKED
One clue for my view: the cost can be proportional to both thickness and length but with different proportionality constants. I mean, to me: Cost=a*thickness+b*length^2 not Cost=a*(thickness+length^2) Thank u.
_________________
The sky is the limit 800 is the limit
GMAT Club Premium Membership  big benefits and savings



Manager
Joined: 10 Aug 2009
Posts: 129

Re: The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
07 Sep 2009, 12:46
1
This post received KUDOS
1
This post was BOOKMARKED
I think the cost function is the following:
\(C=k\times t\times l^2\) tthickness llength
then each statement alone is sufficient
stmt1 \(4\times 0.2\times k=4\times 0.1\times k +160\) you can solve for k sufficient
stmt2 is basically similar to stmt 1... \(9\times 0.1\times k=4\times 0.1\times k +200\) you cansolve for k sufficient



VP
Joined: 16 Jul 2009
Posts: 1476
Schools: CBS
WE 1: 4 years (Consulting)

Re: The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
07 Sep 2009, 13:08
LenaA wrote: I think the cost function is the following:
\(C=k\times t\times l^2\) tthickness llength
then each statement alone is sufficient
stmt1 \(4\times 0.2\times k=4\times 0.1\times k +160\) you can solve for k sufficient
stmt2 is basically similar to stmt 1... \(9\times 0.1\times k=4\times 0.1\times k +200\) you cansolve for k sufficient In fact, that is the formula in order to be D the correct answer (as it is). But my point is, that in a very strict point of view, the proportionality constant (what you mean k), can be different for t and l, that is: Cost=k1*t+k2*l^2. So you need both statements to solve for k1 and k2, and correct answer is C. To sum up, correct answer is C. OA is D.
_________________
The sky is the limit 800 is the limit
GMAT Club Premium Membership  big benefits and savings



Manager
Joined: 10 Aug 2009
Posts: 129

Re: The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
07 Sep 2009, 14:06
2
This post received KUDOS
1
This post was BOOKMARKED
you are wrong. i would suggest to research about the jointly proportional functions. if z is proptional to x (when y is constant) and z is propotional to y (when x is constant), then z is propotional to the product xy and is of the form z=Kxy



VP
Joined: 16 Jul 2009
Posts: 1476
Schools: CBS
WE 1: 4 years (Consulting)

Re: The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
07 Sep 2009, 14:20
LenaA wrote: you are wrong. i would suggest to research about the jointly proportional functions. if z is proptional to x (when y is constant) and z is propotional to y (when x is constant), then z is propotional to the product xy and is of the form z=Kxy Correct. Thank u. Dont know in what i was thinking about! D is the one
_________________
The sky is the limit 800 is the limit
GMAT Club Premium Membership  big benefits and savings



Intern
Joined: 03 Sep 2009
Posts: 29

Re: The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
07 Sep 2009, 14:32
We have only one value missing (here it's K) so it's sure that each statement is sufficient. noboru wrote: LenaA wrote: you are wrong. i would suggest to research about the jointly proportional functions. if z is proptional to x (when y is constant) and z is propotional to y (when x is constant), then z is propotional to the product xy and is of the form z=Kxy Correct. Thank u. Dont know in what i was thinking about! D is the one



Manager
Joined: 27 Feb 2012
Posts: 136

Re: The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
19 Jan 2013, 02:01
2
This post received KUDOS
kiyo0610 wrote: The cost of a square slab is proportional to its thickness and also proportional to the square of its length. What is the cost of a square slab that is 3 meters long and 0.1 meter thick?
(1)The cost of a square slab that is 2 meters long and 0.2 meter thick is $160 more than the cost of a square slab that is 2 meters long and 0.1 meter thick. (2)The cost of a square slab that is 3 meters long and 0.1 meter thick is $200 more than the cost of a square slab that is 2 meters long and 0.1 meter thick. Cost C 1) C proportional to Thickness t 2) C proportional to Length square l^2 C = K t l^2 We need to know constant K to find the answer. Option 1: C1 and C2 difference is given for some thickness and length. We can find the constant Option 2: Same as option1
_________________

Please +1 KUDO if my post helps. Thank you.



Current Student
Status: Everyone is a leader. Just stop listening to others.
Joined: 22 Mar 2013
Posts: 952
Location: India
GPA: 3.51
WE: Information Technology (Computer Software)

Re: The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
09 Sep 2013, 06:04
I formed equation for cost as : C prop to l^2 C prop to t C = kl^2 + rt l= for length t= for thickness. k and r constant of respective proportionality. But in above mentioned solution it is taken as product. I am not 100% satisfied with the derived proportionality as the product of length and thickness. May be I am not able to identify the keyword in the question which governs product of two variables. Or lacking some basic concept, kindly help me to interpret the language of question into a equation. Please also share any theoretical stuff, which I should refer to understand concept of proportionality. Thanks
_________________
Piyush K
 Our greatest weakness lies in giving up. The most certain way to succeed is to try just one more time. ― Thomas A. Edison Don't forget to press> Kudos My Articles: 1. WOULD: when to use?  2. All GMATPrep RCs (New) Tip: Before exam a week earlier don't forget to exhaust all gmatprep problems specially for "sentence correction".



Intern
Joined: 18 Aug 2013
Posts: 18

Re: The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
11 Sep 2013, 04:12
When I first attempted to solve this problem I was a little thrown off by the question just saying proportional, and not directly proportional or indirectly proportional. I now realize that solving this problem is independent of the direct vs. indirect, you may get different values for the cost, but regardless you'll be able to get a value => sufficient.
My question is, can you assume that it's directly proportional from the question stem? Looking at a few of the answers above, it seems that some people have. If this was a P.S. problem instead of a D.S., the answer would depend on this assumption.
Thanks in advance for any help. Grant



Director
Joined: 29 Nov 2012
Posts: 854

Re: The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
27 Oct 2013, 02:32
1
This post received KUDOS
1
This post was BOOKMARKED
Cost is equal to C = X t l^2, where X is a constant, L is length and t is thickness FS 1=> \(X ( 0.2) (2^2)  X (0.1) (2^2) = 160\) => \(X=400\) We can solve for X its sufficient FS 2=> \(X (0.1) (3^2)  X (0.1) (2^2) = 200\)=> \(X=400\)
_________________
Click +1 Kudos if my post helped...
Amazing Free video explanation for all Quant questions from OG 13 and much more http://www.gmatquantum.com/og13th/
GMAT Prep software What if scenarios http://gmatclub.com/forum/gmatprepsoftwareanalysisandwhatifscenarios146146.html



Intern
Joined: 05 Jan 2015
Posts: 13

Re: The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
17 Jan 2015, 17:50
The cost of a square slab is proportional to its thickness and also proportional to the square of its length. What is the cost of a square slab that is 3 meters long and 0.1m thick.
(1) The cost of a square slab that is 2 meters long and 0.2 m thick is $160 more than the cost of a slab that is 2m long and 0.1 m thick
(2) The cost of a square slab that is 3 meters long and 0.1 m thick is 200 more than the cost of a square slab that is 2m long and 0.1 m thick
I read over this on multiple forums and have come to understand why the correct answer is correct.
That is this question can be written as C = kAT where C is cost, A is area, and T is thickness. The wording of the problem essentially states that C is jointly proportional to A and T.
I (and I think a few others) chose to interpret the question as C = kA + mT, where there are now two proportionality constants defining the relationship. At first glance this seems like what the question is leading into, but alas is not the OA.
So based on the original wording of the question we can surmise the relationship is C=kAT. But what wording do you use then to describe the second relationship C = kA + mT? This way I know how to distinguish between these two types of relationships described.



Intern
Joined: 09 May 2013
Posts: 15

Re: The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
18 Jan 2015, 00:17
1
This post received KUDOS
Kevin, In the case you mentioned, the wording should be something like "The cost of stone slab is dependent on its area and height" this can be interpreted as "C= kA + mT
But when it is mentioned that cost is "proportional" to any particular factor, then that implies a multiplicative relation only.
Further, on a lighter note: in the relation C= kA+mT; there can still be a cost even when one of A or T is zero!! So, I feel that even this fact indicates toward a relation like C= kAT
Hope it helps!



Director
Joined: 26 Oct 2016
Posts: 682
Location: United States
Concentration: Marketing, International Business
GPA: 4
WE: Education (Education)

Re: The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
04 Feb 2017, 03:02
cost of slab=(l^2)*t*k where k is the constant of proportionality. we need this k to be able to arrive at the cost. 1) 4*0.2*k=4*0.1*k+160 =>4*0.1*k=160 we can solve for k, the proportionality constant and compute the cost of the slab in the stimulus. sufficient 2) 9*0.1*k4*0.1*k=200 =>0.1k(94)=200 =>k=200/(5*0.1) we can compute the cost of the given slab in the stimulus. sufficient hence D
_________________
Thanks & Regards, Anaira Mitch



NonHuman User
Joined: 09 Sep 2013
Posts: 13828

Re: The cost of a square slab is proportional to its thickness and also [#permalink]
Show Tags
06 Feb 2018, 15:31
Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up  doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources




Re: The cost of a square slab is proportional to its thickness and also
[#permalink]
06 Feb 2018, 15:31






