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

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

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?

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

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