Find the geometric mean between 7 & 11. select one:
a. 4√6 or appx. 9.8
b. 170/18 or appx 9.4
c. √77 or appx. 8.8
d. 9

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:



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:



Therefore for this question n = 2, since there are two numbers. Substituting in:

= = 8.77496438739 ≈ 8.8 (2sf)