I have already got help with figuring this out. But i seem to be getting something wrong so maybe someone can check this over and tell me what im doing wrong

Q) find the angular momentum of a cone with heigh H and radius R

now i was helped and told

Rc = int (x)dv / int dV where (x)dV is the volume element and int dV is the mass density

now dV = pi (rx/h)^2 for a cone

so i did angular momentum = int (r^2)dV / int dV

where int (r^2)dV = pi int of (r^4 x^2 / h^2) dR
= pi (r^5 X^2 / 5 h^2)

and

mass density = pi ( r^3 x^2 / 3 h^2)

so I = 3/5 r^2

but im getting froma book I = 3/10 m r^2 for a cone