Question 893227
Find the volume of the new part.
The volume is the difference of the two circular areas multiplied by the thickness.
{{{V=(A[2]-A[1])t=pi(R[2]^2-R[1]^2)t=pi(15.75^2-3.75^2)(4.5)}}}
{{{V=1053pi}}}{{{mm^3}}}
Converting to {{{m^3}}},
{{{V=1053pi*10^(-9)}}}{{{m^3}}}
The mass in kg would be 
{{{m=20.2/1000=2.02*10^(-2)}}}{{{kg}}}
So the density is,
{{{rho=m/V=(2.02*10^(-2))/(1053pi*10^(-9))}}}
{{{rho=6106}}}{{{kg/m^3}}}