A question about operator overloading

I have a 3D vector class. I have overloaded operator *= such that it can take a scaler value on the right hand side. That is working fine.

Now I have a second loaded operator* which takes a Vector3D arg AND a scaler arg.

So, it would work thus:

Vector3D scaledVec = oldVec * 3.0;

My question is, how would I make the operation commutative such that the following would also be valid:

Vector 3D scaledVec = 3.0 * oldVec;

Must I overload the function?

Create a global overloaded version of the function, something like

operator* ( double , Vector3D& )

I'm in the middle of studying for a psychology test, so if I'm talking rubbish, ignore me. :D