derive the poiseuille's formula dimensionly

As coefficient of viscocity(η)=$\frac{Tangential stress}{Velocity gradient}$=$\frac{F/A}{v/l}$=$\frac{Fl}{vA}$=[MLT^-2][L]/[LT^-1][L²]=[ML^-1T^-1]
Put the dimensions of r⁴,l,p and η in the poiseuille's formula:-
we get:-
V=[M⁰L³T^-1]
As V is the volume passing per second, the dimensions are equated.