If radius of a vessel is doubled then the blood flow is increased by?

Ans. B 16 timesRef: Ganong: 26th ed. P 563* The influence of lumen diameter on resistance is dramatic. This is because resistance is inversely proportional to the radius of the blood vessel (one-half of the vessels diameter) raised to the fourth power (R=1/r4).* This means, that if an artery or arteriole constricts to one-half of its original radius, the resistance to flow will increase 16 times. And if an artery or arteriole dilates to twice its initial radius, then resistance in the vessel will decrease to 1/16 of its original value and flow will increase 16 times.