# Harmonic mean of $$$9$$$, $$$13$$$

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### Your Input

**Find the harmonic mean of $$$9$$$, $$$13$$$.**

### Solution

The harmonic mean of data is given by the formula $$$H = \frac{n}{\sum_{i=1}^{n} \frac{1}{x_{i}}}$$$, where $$$n$$$ is the number of values and $$$x_i, i=\overline{1..n}$$$ are the values themselves.

Since we have $$$2$$$ points, $$$n = 2$$$.

The sum of the reciprocals of the values is $$$\frac{1}{9} + \frac{1}{13} = \frac{22}{117}$$$.

Therefore, the harmonic mean is $$$H = \frac{2}{\frac{22}{117}} = \frac{117}{11}$$$.

### Answer

**The harmonic mean is $$$\frac{117}{11}\approx 10.636363636363636$$$A.**