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

It is currently 19 Apr 2014, 22:18

Close

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

The useful life of a certain piece of equipment is

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
Joined: 11 Aug 2009
Posts: 129
Followers: 1

Kudos [?]: 14 [0], given: 3

GMAT Tests User
The useful life of a certain piece of equipment is [#permalink] New post 18 Nov 2009, 20:47
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

73% (01:27) correct 26% (00:28) wrong based on 15 sessions
The useful life of a certain piece of equipment is determined by the following formula: u =(8d)/h^2, where u is the useful life of the equipment, in years, d is the density of the underlying material, in g/cm3, and h is the number of hours of daily usage of the equipment. If the density of the underlying material is doubled and the daily usage of the equipment is halved, what will be the percentage increase in the useful life of the equipment?

A. 300%
B. 400%
C. 600%
D. 700%
E. 800%

OPEN DISCUSSION OF THIS QUESTION IS HERE: the-useful-life-of-a-certain-piece-of-equipment-is-determine-101496.html
[Reveal] Spoiler: OA

Last edited by kairoshan on 19 Nov 2009, 05:45, edited 1 time in total.
Kaplan GMAT Prep Discount CodesKnewton GMAT Discount CodesGMAT Pill GMAT Discount Codes
Senior Manager
Senior Manager
Joined: 31 Aug 2009
Posts: 423
Location: Sydney, Australia
Followers: 6

Kudos [?]: 91 [0], given: 20

GMAT Tests User
Re: The useful life of a certain piece of equipment is determine [#permalink] New post 19 Nov 2009, 00:48
Assuming you mean h^2 then we have:

Original useful life: u=8d/h^2
New useful life: u=\frac{8(2d)}{(h/2)^2}=\frac{64d}{h^2}
Amount Increase = new - old = \frac{64d}{h^2}-\frac{8d}{h^2}=\frac{56}{h^2}
Increase/Original = \frac{56d}{h^2}/\frac{8d}{h^2}
= 7.

To get percentage multiple by 100 = 700%
Ans = D
Manager
Manager
User avatar
Joined: 06 Sep 2009
Posts: 115
Followers: 2

Kudos [?]: 17 [0], given: 3

Re: The useful life of a certain piece of equipment is determine [#permalink] New post 19 Nov 2009, 01:36
It is not a DS problem, but that's OK.

I understood by two ways:

1) U = 8d/hˆ2

U' = 8*2d/ (1/2*h)ˆ2 = 64d/hˆ2 --> U *64 = U ' --> 700% increase

Ans: D

2) U = 8d/(2h)

U '= 8*2d/(2*(1/2)*d) = 16d/h --> 300% increase

Ans A
Manager
Manager
Joined: 11 Aug 2009
Posts: 129
Followers: 1

Kudos [?]: 14 [0], given: 3

GMAT Tests User
Re: The useful life of a certain piece of equipment is determine [#permalink] New post 19 Nov 2009, 05:46
diogoguitarrista wrote:
It is not a DS problem, but that's OK.

I understood by two ways:

1) U = 8d/hˆ2

U' = 8*2d/ (1/2*h)ˆ2 = 64d/hˆ2 --> U *64 = U ' --> 700% increase

Ans: D

2) U = 8d/(2h)

U '= 8*2d/(2*(1/2)*d) = 16d/h --> 300% increase

Ans A


OA is D. sorry. I just edited the question.
Manager
Manager
Joined: 29 Mar 2010
Posts: 141
Location: United States
Concentration: Finance, International Business
GMAT 1: 590 Q28 V38
GPA: 2.54
WE: Accounting (Hospitality and Tourism)
Followers: 1

Kudos [?]: 22 [0], given: 12

GMAT ToolKit User
Re: The useful life of a certain piece of equipment is [#permalink] New post 04 May 2013, 16:03
In this problem why does it become (64h^2)/h^2 instead of (32h^2)/h^2
_________________

4/28 GMATPrep 42Q 36V 640

Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 17321
Followers: 2875

Kudos [?]: 18405 [0], given: 2350

GMAT Tests User CAT Tests
Re: The useful life of a certain piece of equipment is [#permalink] New post 05 May 2013, 03:21
Expert's post
Re: The useful life of a certain piece of equipment is   [#permalink] 05 May 2013, 03:21
    Similar topics Author Replies Last post
Similar
Topics:
New posts A rope of 40 meter long cut into 2 pieces, one piece is used SunShine 2 09 Feb 2006, 06:42
New posts A 40 meter long wire is cut into 2 pieces. one piece is used Gordon 7 12 Mar 2006, 09:33
This topic is locked, you cannot edit posts or make further replies. New 1 Experts publish their posts in the topic The useful life of a certain piece of equipment is determine bmwhype2 6 20 Feb 2008, 14:00
New posts useful life skim 1 27 Jun 2009, 10:36
New posts 1 Experts publish their posts in the topic The useful life of a certain piece of equipment is determine bruiz 4 22 Sep 2010, 05:25
Display posts from previous: Sort by

The useful life of a certain piece of equipment is

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.