Trouble with a problem. What is the flow rate if a tube consists of two sections, the first with a length of 20cm and radius 0.15cm and the second part with length 1.0cm radius 0.05? with a pressure difference across the entire tube of 3cmHg (p1-p3). (viscosity = 0.801 cP) I've tried this and end up with two many unknowns and not enough equations. Can anybody help?