Question 1041490
The original cylinder has a volume of 
{{{V[cyl]=pi*R^2*H}}}.
The cone using the same base radius and height has a volume of,
{{{V[cone]=(pi/3)*R^2*H}}}
So to go from cylinder to cone you need to remove this volume of wood,
{{{V=V[cyl]-V[cone]}}}
{{{V=pi*R^2*H-(pi/3)R^2*H}}}
{{{V=((2pi)/3)R^2*H}}}
{{{V=(2/3)V[cyl]}}}