1)
V=hpr^2
r=√(V/(hp)), using 216p for V and 3 ft for h you get:
r=√(216p/(3p))
r=√72
r≈8.5 ft (to nearest tenth of a foot)
2)
The volume of these ice cream cones is half the volume of a sphere plus the volume of a cone...
V=((4pr^3)/3)/2+(hpr^2)/3
V=(4pr^3)/6+(hpr^2)/3
V=(p/3)(2r^3+hr^2)
And the difference between them is:
V=(p/3)(2R^3+HR^2-2r^3-hr^2), given R,H,r,h=3,12,2,8:
V=(p/3)(2*27+12*9-2*8-8*4)
V=(p/3)(114)
V=38p cm^3
V≈119.38 cm^3 (to nearest one-hundredth of a cm^3)
3)
V=[(4pr^3)/3]/2
V=(2pr^3)/3 and when r=15yd
V=2250p yd^3
V≈7068.58 yd^3 (to nearest hundredth of a yd^3)