The geometric mean is the positive
number x such that:
A
X
X
B
To find the geometric mean:
Example: Find the geometric mean
between 4 and 16.
Write a proportion with X in the two
mean positions:
Find the
Cross multiply: square root,
4
X
X
16
X2 = 64
simplify.
X=8
Another example:
Find the geometric mean between 4
and 20.
4
X
X
20
X2 = 80
X=
80
X=4 5
What if you know the geometric mean?
Example: 6 is the geometric mean
between 9 and what other number:
Set up the
proportion
this way:
Cross multiply:
9X = 36
X
6
And finish!
6
9
X = 4 *no square root!!!