The geometric mean is a variation on the standard arithmetic mean (where the numbers are totalled, then divided by the amount totalled). The latter of these two can be generalised as:
[tex] \frac{a_{1} + a_{2} + a_{3} ... + a_{n}}{n} [/tex]
The difference with a geometric mean is that instead of totalling the numbers, the product is found; similarly instead of a division stage at the end, an appropriate root is found:
[tex] sqrt[n]({a_{1}a_{2}a_{3}...a_{n}}) [/tex]
Therefore for this question n = 2, since there are two numbers. Substituting in:
[tex] sqrt{7 * 11} [/tex] = [tex] \sqrt{77}[/tex] = 8.77496438739 ≈ 8.8 (2sf)
