Question

a sphere wall is 20mm thick, inside diameter is 10M. What is the mass of steel if the density is 7850Kgm3?

Answer 1

find volume of the shell
r1 = 10 m = 1000 cm = 10000 mm
V1 = (4/3)π(10000)^3 = ....

r2 = 10000 - 20 = 9980 mm
V2 = (4/3)π(9980)^3 = ....

volume of shell = V1 - V2 = ....

7850 kg/m^3
= 7850000 g/(100^3 cm^3)
= 7.85 g / cm^3
= .00785 g/ mm^3

I will let you do all the button-pushing
Use the memories in your calculator, don't round off any intermediate numbers, let your machine do the work for you