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}.

Answer: E.

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?"