if ball c is 3 times the volume of ball d and ball d has 1/3 the mass of ball c, which has the greater density?

They have same density

Explanation:

The density of an object is defined as

where

m is the mass of the object

V is its volume

Let's call and the mass and the volume of ball C, respectively. Therefore, the density of ball C is:

We know that the volume of ball C is 3 times the volume of ball D, so

And we also know that ball D has 1/3 the mass of ball C:

So, the density of ball D is:

Therefore, the two balls have same density.

see earlier