Question

Find the mean proportional between the following:

$5$ and $20$

Answer 1

Let $x$ be the mean proportion. Then $5,x,\&20$ are in continued proportion.

$b^2=ac$ $\left[b=x,a=5,\&c=20\right]$

$x^2=5\times 20$

$x=\sqrt{100}$

$x=10$

So, $10$ is the mean proportion between $5$ and $20$.