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

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Joined: 02 Dec 2012
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In the expression above, if xn#0, what is the value of S?  [#permalink]

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18 Dec 2012, 08:13
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84% (01:22) correct 16% (01:40) wrong based on 546 sessions

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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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18 Dec 2012, 08:17
1
$$S=\frac{\frac{2}{n}}{\frac{1}{x}+\frac{2}{3x}}$$

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

$$S=\frac{\frac{2}{n}}{\frac{1}{x}+\frac{2}{3x}}=\frac{\frac{2}{n}}{\frac{5}{3x}}=\frac{6x}{5n}$$

(1) x = 2n --> $$S=\frac{6x}{5n}=\frac{6*2n}{5n}=\frac{12}{5}$$. Sufficient.

(2) n = 1/2. We need the value of x to answer the question. Not sufficient.

Answer: A.
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Re: In the expression above, if xn#0, what is the value of S?  [#permalink]

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

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21 Dec 2013, 05:39
steilbergauf wrote:
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!

Your approach is not clear at all. Please show your work. Thank you.
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Re: In the expression above, if xn#0, what is the value of S?  [#permalink]

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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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Posts: 58320
Re: In the expression above, if xn#0, what is the value of S?  [#permalink]

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

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