What is the volume of a hollow ball whose other radius is 200m and inner radius of 100m.
What is the mass if it is iron*

The volume of the hollow ball will be equal to the difference between the volume of a sphere with the outer radius and the volume of a sphere with the inner radius.

Remember that the volume of a sphere of radius R is given by:

V = (4/3)*pi*R^3

where pi = 3.14

Then if R is the outer radius, and r is the inner radius, the volume of the hollow ball is:

V = (4/3)*pi*( R^3 - r^3)

In this case, we have:

R = 200m

r = 100m

Then the volume of the hollow ball is:

V = (4/3)*3.14*( (200m)^3 - (100m)^3)

V = 29,306,666.67 m^3

Now, if this hollow ball is made of iron, we want to find the mass.

Remember the relation:

Mass = Density*Volume.

We know that the density of the iron is:

D = 7300 kg/m^3

Then the mass of this hollow ball is:

M = (7300 kg/m^3)*(29,306,666.67 m^3) = 213,938,666,666.6 kg

goog may have it for you