a 3 inch diameter hole is drilled 6 inch deep?

525((2/3)³ - .5π(1/8)²) + 705(.5π(1/8)²) = 159.97… ≈ 160 lb.

The density of a material is mass/volume so if you want to find the mass then simply multiply by the volume of the material (mass/volume times volume = mass). The volume of the hole (and consequently also the volume of the lead cylinder) is 0.02454 ft^3 so the mass of lead is 17.3 lbs.

The volume of a cube 8in per side is 0.2963 ft^3 so the volume of an 8in cube with a hole such as you have described is 0.2718 ft^3 and the mass of this brass object is 142.67 lbs.

I have used volume of cube = length of side^3 and volume of cylinder = pi*r^2*length (where r is diameter/2), so please check my work to make sure it is correct.

Mass of brass = [{(8/12)^3} - {pi*(1.5/12)^2}*(6/12)]*525 lbs = 142.67 lbs

Mass of lead = [{pi*(1.5/12)^2}*(6/12)]*705 = 17.30

Total mass of the composite cube = 142.67 + 17.30 = 159.97 lbs or 160 lbs

(real world answer. look out) Brass is a general name for combinations of Zinc and Copper. There are 10000s of combinations. You can not get an accurate answer unless you know the composition of the brass.

approx 159 lbs