I am not divisible by anything, but there's a formula to find my value.
I have a 9 in the ten-billionths place.
Multiply me by $d$ to get $c$.
The answer is
$\pi$
Multiply me by $d$ to get $c$.
Pi times the diameter of a circle is the circumference.
I have a 9 in the ten-billionths place.
Pi's decimal value is 3.141592653589...
there's a formula to solve my value.
There are a number of continued fractions that evaluate to $\pi$.