What is the circumference of an 8 inch diameter circle?

##C=8pi##

Just use this: ##C=2piR## The diameter is 8 and the radius is a half of the diameter, so the radius is 4

##C=Circunference## ##pi~=3.14## ##R=radius##

##C=2times3.14times4##

##color(brown)(C~=25.12##

Or you can answer with ##pi## as a multiplicative constant: ##color(red)(C=8pi##