Consider a scenario which involves a stationary machine gun (MG) and a moving target T. MG emits successive bullets at constant time intervals t(e) which hit the moving target at constant time intervals t(r). The bullets move with velocity U and the target with velocity V. The first bullet hits the target at t=0. Equating the distnce traveled by the second bullet with the distance traveled by the target between the reception of the first and of the second bullet we obtain U(t(r)-t(e))=Vt(r) (1) where from t(r)=Ut(e)/(U-V) (2) Replacing the MG with a source of light we obtain t(r)=ct(e)/c-V). We could follow scenarios which lead to an expression containing the terms U+V and c+V. Are U+V, U-V, c+V and c-V the result of a velocity addition?