What is the geometric mean of 8 and 20?

The answer is approximately 12.65. To find the answer of this problem you set 20/x as equal to x/8 (also works vice versa) and then you cross multiply getting 160=x^2. Afterwards you use the order of operations and find that the square root of 160 is equal to x. The square root of 160 is approximately equal to 12.65 which is how you get to your final answer.