find the volume of the cylinder using the mass and its density V = M / D
so Volume = 12.4 / 2.7 = 4.59259259259cm3
Divide by length to get the volume of a 1cm slice: 4.59259259259 / 2 = 2.2962962963
The cross section area in cm2 = the volume in cm3.
Reverse pi r^2 to get the radius, so divide by pi then take the square root.
R = √V / R = 0.85494667244cm
hope that helps
