For any circle, the circumfrence [tex]C=2\pi r=\pi d[/tex] where r is the radius and d is the diameter.
Use 20 inches for our radius in the formula [tex]C=2\pi r[/tex].
[tex]C=2\pi \times20[/tex]
Using π ≈ 3.14...
[tex]C\approx2\times3.14\times20[/tex]
[tex]C\approx6.28\times20[/tex]
[tex]\boxed{C\approx125.6\ inches}[/tex]