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In the expression above, if xn#0, what is the value of S?

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In the expression above, if xn#0, what is the value of S?  [#permalink]

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New post 18 Dec 2012, 08:13
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\(S=\frac{\frac{2}{n}}{\frac{1}{x}+\frac{2}{3x}}\)

In the expression above, if xn ≠ 0, what is the value of S?

(1) x = 2n
(2) n = 1/2
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Re: In the expression above, if xn#0, what is the value of S?  [#permalink]

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New post 18 Dec 2012, 08:17
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Re: In the expression above, if xn#0, what is the value of S?  [#permalink]

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New post 20 Dec 2013, 10:32
Hi guys,

quick question:

I started to simplify the equation by multiplying the denominator such as 2/n (x+3x/2) and did not get the same solution. What is wrong with my approach?

Thanks a lot in advance!
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New post 21 Dec 2013, 05:39
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Re: In the expression above, if xn#0, what is the value of S?  [#permalink]

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New post 21 Dec 2013, 07:54
Hi Bunuel,

sorry for being imprecise and thanks for your quick answer.

I used the following approach:

\(S=\frac{\frac{2}{n}}{\frac{1}{x}+\frac{2}{3x}}\)

\(S= \frac{2}{n}(x+\frac{3x}{2})\)

\(S= \frac{2x}{n}+\frac{6x}{2n}\)

\(S= \frac{4x}{2n}+\frac{6x}{2n}=\frac{5x}{n}\)

Can you please tell me what is wrong with my approach?

Thanks a lot in advance.
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Re: In the expression above, if xn#0, what is the value of S?  [#permalink]

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New post 22 Dec 2013, 06:30
steilbergauf wrote:
Hi Bunuel,

sorry for being imprecise and thanks for your quick answer.

I used the following approach:

\(S=\frac{\frac{2}{n}}{\frac{1}{x}+\frac{2}{3x}}\)

\(S= \frac{2}{n}(x+\frac{3x}{2})\)

\(S= \frac{2x}{n}+\frac{6x}{2n}\)

\(S= \frac{4x}{2n}+\frac{6x}{2n}=\frac{5x}{n}\)

Can you please tell me what is wrong with my approach?

Thanks a lot in advance.


The point is that reciprocal of the denominator is not \(x+\frac{3x}{2}\).

The denominator is \(\frac{1}{x}+\frac{2}{3x}=\frac{3+2}{3x}=\frac{5}{3x}\), thus its reciprocal is \(\frac{3x}{5}\).
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Re: In the expression above, if xn#0, what is the value of S?  [#permalink]

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New post 17 Sep 2019, 05:53
Walkabout wrote:
\(S=\frac{\frac{2}{n}}{\frac{1}{x}+\frac{2}{3x}}\)

In the expression above, if xn ≠ 0, what is the value of S?

(1) x = 2n
(2) n = 1/2


\(S=\frac{\frac{2}{n}}{\frac{1}{x}+\frac{2}{3x}}\)

In the expression above, if xn ≠ 0, what is the value of S?

(1) x = 2n
\(S=\frac{\frac{2}{n}}{\frac{1}{x}+\frac{2}{3x}}\)
\(S=\frac{\frac{2}{n}}{\frac{1}{2n}+\frac{1}{3n}}\)
\(S=\frac{\frac{2}{n}}{\frac{5}{6n}}\)
\(S= \frac{12}{5} = 2.4\)

(2) n = 1/2
Since x is unknown
NOT SUFFICIENT

IMO A
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Re: In the expression above, if xn#0, what is the value of S?   [#permalink] 17 Sep 2019, 05:53
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