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

It is currently 22 Oct 2014, 20:43

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

Challenge 25 Question (derived rate problem)

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
User avatar
Joined: 17 Dec 2005
Posts: 162
Followers: 1

Kudos [?]: 7 [0], given: 0

Challenge 25 Question (derived rate problem) [#permalink] New post 31 May 2006, 15:08
Hello everyone,

This question is from the challenge 25 (i believe). I don't completely understand the explanation. Can someone please explain? Thanks.

The gold depreciated at a rate of X% per year between 2000 and 2005. If the gold cost S dollars in 2001 and T dollars in 2003, how much did it cost in 2002?

Thanks again.

Mike
Senior Manager
Senior Manager
avatar
Joined: 15 Mar 2005
Posts: 423
Location: Phoenix
Followers: 1

Kudos [?]: 9 [0], given: 0

Re: Challenge 25 Question (derived rate problem) [#permalink] New post 31 May 2006, 16:16
If gold costs S in 2001 and T in 2003 and is steadily depreciating at X%,
T = S*(1-X/100)^2 .................A
After a year of 2001 (when gold was S), in 2002, the gold would cost S(1-X/100) .............................B

Therefore, gold in 2002
= S*(T/S)^1/2 = (S^1/2)/T.

In a simpler way, you can see it as a GP.
S Sr Sr^2, where r = (1-X/100).
Since Sr^2 = T, r = (T/S)^(1/2).
Therefore, Sr = S*(T/S)^(1/2) = (S^(1/2))/T
_________________

Who says elephants can't dance?

VP
VP
User avatar
Joined: 29 Dec 2005
Posts: 1351
Followers: 7

Kudos [?]: 28 [0], given: 0

Re: Challenge 25 Question (derived rate problem) [#permalink] New post 31 May 2006, 16:32
kapslock wrote:
If gold costs S in 2001 and T in 2003 and is steadily depreciating at X%,
T = S*(1-X/100)^2 .................A
After a year of 2001 (when gold was S), in 2002, the gold would cost S(1-X/100) .............................B

Therefore, gold in 2002: = S*(T/S)^1/2 = (S^1/2)/T.

In a simpler way, you can see it as a GP.
S Sr Sr^2, where r = (1-X/100).
Since Sr^2 = T, r = (T/S)^(1/2).
Therefore, Sr = S*(T/S)^(1/2) = (S^(1/2))/T


great work.

but i guess, S*(T/S)^1/2 = (ST)^1/2.

How you arrived here? "Gold in 2002 = = S*(T/S)^1/2 = (S^1/2)/T."?
Senior Manager
Senior Manager
avatar
Joined: 15 Mar 2005
Posts: 423
Location: Phoenix
Followers: 1

Kudos [?]: 9 [0], given: 0

Re: Challenge 25 Question (derived rate problem) [#permalink] New post 31 May 2006, 21:28
Professor wrote:
kapslock wrote:
If gold costs S in 2001 and T in 2003 and is steadily depreciating at X%,
T = S*(1-X/100)^2 .................A
After a year of 2001 (when gold was S), in 2002, the gold would cost S(1-X/100) .............................B

Therefore, gold in 2002: = S*(T/S)^1/2 = (S^1/2)/T.

In a simpler way, you can see it as a GP.
S Sr Sr^2, where r = (1-X/100).
Since Sr^2 = T, r = (T/S)^(1/2).
Therefore, Sr = S*(T/S)^(1/2) = (S^(1/2))/T


great work.

but i guess, S*(T/S)^1/2 = (ST)^1/2.

How you arrived here? "Gold in 2002 = = S*(T/S)^1/2 = (S^1/2)/T."?


Good catch Prof. My mind was not properly working - that's what happens when you're solving GMAT problems at work :)
_________________

Who says elephants can't dance?

Manager
Manager
User avatar
Joined: 17 Dec 2005
Posts: 162
Followers: 1

Kudos [?]: 7 [0], given: 0

question regarding the final step [#permalink] New post 31 May 2006, 23:33
Hello,

This may not be the most intelligent question but...

how does S*(T/S)^1/2 = (ST)^1/2 ?

If you have sqrt (T/S) * S, where <i>sqrt (T/S)</I> represents the rate of decline expressed in T and S, does that come out to sqrt(ST)?

Thanks.

Mike
Senior Manager
Senior Manager
avatar
Joined: 15 Mar 2005
Posts: 423
Location: Phoenix
Followers: 1

Kudos [?]: 9 [0], given: 0

Re: question regarding the final step [#permalink] New post 01 Jun 2006, 03:42
mrmikec wrote:
Hello,

This may not be the most intelligent question but...

how does S*(T/S)^1/2 = (ST)^1/2 ?

If you have sqrt (T/S) * S, where <i>sqrt (T/S)</I> represents the rate of decline expressed in T and S, does that come out to sqrt(ST)?

Thanks.

Mike


Sqrt (T/S) * S
= { Sqrt(T)/Sqrt(S) } * S
= Sqrt (T) * S/Sqrt(S)
= Sqrt (T) * Sqrt (S)
= Sqrt (ST)

Hope that helps.
_________________

Who says elephants can't dance?

Manager
Manager
User avatar
Joined: 17 Dec 2005
Posts: 162
Followers: 1

Kudos [?]: 7 [0], given: 0

Re: question regarding the final step [#permalink] New post 01 Jun 2006, 09:23
kapslock wrote:
mrmikec wrote:
Hello,

This may not be the most intelligent question but...

how does S*(T/S)^1/2 = (ST)^1/2 ?

If you have sqrt (T/S) * S, where <i>sqrt (T/S)</I> represents the rate of decline expressed in T and S, does that come out to sqrt(ST)?

Thanks.

Mike


Sqrt (T/S) * S
STEP 2 = { Sqrt(T)/Sqrt(S) } * S
= Sqrt (T) * S/Sqrt(S)
= Sqrt (T) * Sqrt (S)
= Sqrt (ST)

Hope that helps.



This is helpful. Thank you.

One claification though on Step 2- > [ Sqrt(T/S) * S = Sqrt(T)*Sqrt(1/S)*S ] ? Correct?
Re: question regarding the final step   [#permalink] 01 Jun 2006, 09:23
    Similar topics Author Replies Last post
Similar
Topics:
3 Experts publish their posts in the topic Problems with Work/Rate questions marijose 8 11 Feb 2011, 07:20
Challenge 25 - 5 questions - Please Advice! successstory 1 09 Nov 2006, 21:52
Challenge 25 - 5 questions successstory 2 08 Nov 2006, 12:22
challenge 25 QUESTION 22 mand-y 5 31 May 2006, 13:37
challenge 25 question 2 mand-y 5 31 May 2006, 11:36
Display posts from previous: Sort by

Challenge 25 Question (derived rate problem)

  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®.