When blood flows along a blood vessel, the flux $F$ (the volume of blood per unit time that flows past a given point) is proportional to the fourth power of the radius $R$ of the blood vessel: $F=kR^4$ (Poiseuille's Law).

A partially clogged artery can be expanded by an operation called angioplasty, in which a balloon-tipped catheter is inflated inside the artery in order to widen it and restore the normal blood flow.

It can be shown (do it) that the relative change in $F$ is about four times the relative change in $R$. So, how will a $5$% increase in the radius affect the flow of blood?

percent increase in blood flow.