How Do You Calculate the Mass of an Osmium Sphere?

[Mootiek]

I am having trouble with how to set up the equation for this problem...

Os is the densest element known. Given that the density of Os is 22.57g/cm^3, calculate the mass, in kg, of an Os sphere 15 cm in diameter, which is about the size of a grapefruit.

Any help would be greatly appreciated. I am really confused with where the diameter fits in... I feel so lost in this class! Yikes!

 

[Point Conception]

You need to work on the basics:
Volume of a sphere = 4/3( pi ) (radius cubed)
Density = mass/volume