Question

If the arithmetic mean of 7, 9, 11, 13, x, 21 is 13, find the value of x.

Answer 1

Observations: 7, 9, 11, 13, x, 21
Given:
Mean = 13
We know:

$\mathrm{Mean}=\frac{\mathrm{Sum}\mathrm{of}\mathrm{observa}\mathrm{tions}}{\mathrm{Number}\mathrm{of}\mathrm{observations}}$

Thus, we have:

$$\begin{gathered} 13=\frac{7+9+11+13+x+21}{6} \\ \Rightarrow 13=\frac{61+x}{6} \\ \Rightarrow 78=61+x \\ \Rightarrow x=17 \end{gathered}$$