Hello!

Denote the radius of a can in cm as `R.`

Removed oil had the shape of a disk (upright circular cylinder). Its height `h=10 cm` is given, its volume `V=3000 cm^3` is also given. The relation between them is

`V=pi*R^2*h,`

so

`R=sqrt(V/(pi*h)) approx sqrt(3000/(3.14*10)) approx 9.77 (cm).`

This is the answer.