$G = \exp\left(\frac{1}{n}\sum_{i=1}^n \ln(x_i)\right)$

$G = \left(\prod_{i=1}^n x_i\right)^{1/n}$

$\log_{10}(G) = \frac{1}{n}\sum_{i=1}^n \log_{10}(x_i)$

$G = \frac{n}{\sum_{i=1}^n \frac{1}{x_i}}$