Acone has a radius of 6 inches and a height of 20 inches what is the exact volume of the cone

The volume of any cone is    (1/3) (π) (radius²) (height)

For this cone,        Volume = (1/3) (π) (6 inches)² (20 inches)

                                             = (1/3) (π) (36 inches²) (20 inches)

                                             =    240 π cubic inches .

In order to give you the 'exact' volume that you asked for,
I have to leave ' π ' in there.  ' π ' is an irrational number,
so there's no way to write it exactly with digits, and that
means that no number that involves π can every be written
exactly with digits.

We can approximate π with any accuracy we want, and so
we can give you the volume with any accuracy you want.
But if we can't use the symbol for π, we can never be exact.,
no matter how many million decimal places we write.