Question 233498
Your formula is for a Right Circular cone, you are solving a Frustum of a Right Circular cone. The part of a right circular cone between the base and a plane parallel to the base whose distance from the base is less than the height of the cone.
V=Pi(R^2+rR+r^2)h/3
V=3.14(1.5^2+1*1.5+1^2)h/3
V=3.14(2.25+2+1)4/3
V=3.14*5.25*4/3
V=65.94/3
V=21.98 cu in