A bicycle has a radius of 30 what? Once you have the units for the radius, multiply the radius by . Using 3.14 for should be plenty close enough, although is a very precise (6 decimal place) rational approximation. Once you have done the arithmetic with the units given for the radius, convert to millimeters. THEN, and only then, round off.
John
My calculator said it, I believe it, that settles it
