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m25 #6

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Manager
Status: Current MBA Student
Joined: 19 Nov 2009
Posts: 127
Concentration: Finance, General Management
GMAT 1: 720 Q49 V40
Followers: 13

Kudos [?]: 274 [0], given: 210

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04 Jan 2011, 12:29
I got this problem correct during the test by plugging in values and testing. I would like to learn the algebra. Please advise. Thanks.

Gold depreciated at a rate of $$X%$$ per year between 2000 and 2005. If 1 kg of gold cost $$S$$ dollars in 2001 and $$T$$ dollars in 2003, how much did it cost in 2002?

a. $$T\frac {S}{2}$$
b. $$T\sqrt{\frac{T}{S}}$$
c. $$T\sqrt{S}$$
d. $$T\frac{S}{\sqrt {T}}$$
e. $$\sqrt{ST}$$
Math Expert
Joined: 02 Sep 2009
Posts: 34438
Followers: 6257

Kudos [?]: 79469 [1] , given: 10018

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04 Jan 2011, 13:13
1
KUDOS
Expert's post
tonebeeze wrote:
I got this problem correct during the test by plugging in values and testing. I would like to learn the algebra. Please advise. Thanks.

Gold depreciated at a rate of $$X%$$ per year between 2000 and 2005. If 1 kg of gold cost $$S$$ dollars in 2001 and $$T$$ dollars in 2003, how much did it cost in 2002?

a. $$T\frac {S}{2}$$
b. $$T\sqrt{\frac{T}{S}}$$
c. $$T\sqrt{S}$$
d. $$T\frac{S}{\sqrt {T}}$$
e. $$\sqrt{ST}$$

Price of 1kg gold in 2001 - $$S$$;
Price of 1kg gold in 2002 - $$S(1-\frac{x}{100})$$;
Price of 1kg gold in 2003 - $$S(1-\frac{x}{100})^2=T$$ --> $$(1-\frac{x}{100})=\sqrt{\frac{T}{S}}$$;

Price of 1kg gold in 2002 - $$S(1-\frac{x}{100})=S*\sqrt{\frac{T}{S}}=\sqrt{ST}$$.

_________________
Intern
Joined: 16 Sep 2012
Posts: 15
Concentration: Finance, General Management
GMAT 1: 710 Q47 V41
Followers: 0

Kudos [?]: 6 [0], given: 2

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29 Jun 2013, 03:56
Bunuel wrote:
tonebeeze wrote:
I got this problem correct during the test by plugging in values and testing. I would like to learn the algebra. Please advise. Thanks.

Gold depreciated at a rate of $$X%$$ per year between 2000 and 2005. If 1 kg of gold cost $$S$$ dollars in 2001 and $$T$$ dollars in 2003, how much did it cost in 2002?

a. $$T\frac {S}{2}$$
b. $$T\sqrt{\frac{T}{S}}$$
c. $$T\sqrt{S}$$
d. $$T\frac{S}{\sqrt {T}}$$
e. $$\sqrt{ST}$$

Price of 1kg gold in 2001 - $$S$$;
Price of 1kg gold in 2002 - $$S(1-\frac{x}{100})$$;
Price of 1kg gold in 2003 - $$S(1-\frac{x}{100})^2=T$$ --> $$(1-\frac{x}{100})=\sqrt{\frac{T}{S}}$$;

Price of 1kg gold in 2002 - $$S(1-\frac{x}{100})=S*\sqrt{\frac{T}{S}}=\sqrt{ST}$$.

Thank you for posting and including into GMAT Club free test.
I find the phrasing of the question obscure: all three parameters (i.e. S, T and X%) are included as known parameters.
But then the question asks to express 2002 value in terms of S and T (and not X%) which only becomes clear when you look at the answers.
I suggest the following rephrasing: "how much did it cost in 2002 in terms of S and T?"
Math Expert
Joined: 02 Sep 2009
Posts: 34438
Followers: 6257

Kudos [?]: 79469 [0], given: 10018

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29 Jun 2013, 04:01
NikRu wrote:
Bunuel wrote:
tonebeeze wrote:
I got this problem correct during the test by plugging in values and testing. I would like to learn the algebra. Please advise. Thanks.

Gold depreciated at a rate of $$X%$$ per year between 2000 and 2005. If 1 kg of gold cost $$S$$ dollars in 2001 and $$T$$ dollars in 2003, how much did it cost in 2002?

a. $$T\frac {S}{2}$$
b. $$T\sqrt{\frac{T}{S}}$$
c. $$T\sqrt{S}$$
d. $$T\frac{S}{\sqrt {T}}$$
e. $$\sqrt{ST}$$

Price of 1kg gold in 2001 - $$S$$;
Price of 1kg gold in 2002 - $$S(1-\frac{x}{100})$$;
Price of 1kg gold in 2003 - $$S(1-\frac{x}{100})^2=T$$ --> $$(1-\frac{x}{100})=\sqrt{\frac{T}{S}}$$;

Price of 1kg gold in 2002 - $$S(1-\frac{x}{100})=S*\sqrt{\frac{T}{S}}=\sqrt{ST}$$.

Thank you for posting and including into GMAT Club free test.
I find the phrasing of the question obscure: all three parameters (i.e. S, T and X%) are included as known parameters.
But then the question asks to express 2002 value in terms of S and T (and not X%) which only becomes clear when you look at the answers.
I suggest the following rephrasing: "how much did it cost in 2002 in terms of S and T?"

Thank you for the suggestion.
_________________
Math Expert
Joined: 02 Sep 2009
Posts: 34438
Followers: 6257

Kudos [?]: 79469 [0], given: 10018

Show Tags

29 Jun 2013, 04:11
NikRu wrote:
Bunuel wrote:
tonebeeze wrote:
I got this problem correct during the test by plugging in values and testing. I would like to learn the algebra. Please advise. Thanks.

Gold depreciated at a rate of $$X%$$ per year between 2000 and 2005. If 1 kg of gold cost $$S$$ dollars in 2001 and $$T$$ dollars in 2003, how much did it cost in 2002?

a. $$T\frac {S}{2}$$
b. $$T\sqrt{\frac{T}{S}}$$
c. $$T\sqrt{S}$$
d. $$T\frac{S}{\sqrt {T}}$$
e. $$\sqrt{ST}$$

Price of 1kg gold in 2001 - $$S$$;
Price of 1kg gold in 2002 - $$S(1-\frac{x}{100})$$;
Price of 1kg gold in 2003 - $$S(1-\frac{x}{100})^2=T$$ --> $$(1-\frac{x}{100})=\sqrt{\frac{T}{S}}$$;

Price of 1kg gold in 2002 - $$S(1-\frac{x}{100})=S*\sqrt{\frac{T}{S}}=\sqrt{ST}$$.

Thank you for posting and including into GMAT Club free test.
I find the phrasing of the question obscure: all three parameters (i.e. S, T and X%) are included as known parameters.
But then the question asks to express 2002 value in terms of S and T (and not X%) which only becomes clear when you look at the answers.
I suggest the following rephrasing: "how much did it cost in 2002 in terms of S and T?"

Done. Edited. Thank you again.
_________________
Re: m25 #6   [#permalink] 29 Jun 2013, 04:11
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m25 #6

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