 Hello and welcome to the session. In this session, we will discuss about the first term of a right circular cone. Given a right circular cone which is sliced through by a plane to its base, as you can see here that this cone is being sliced by a plane which is parallel to the base of the cone. Now when the smaller conical portion is removed, as you can see we have removed the smaller conical portion. The resulting solid is called a frustum of a right circular cone. That is this solid portion is called the frustum of right circular cone. Now we shall discuss various formula involving the frustum of a cone. First we have the volume of a frustum of a cone. This is given by 1 upon 3 pi h multiplied by r1 square plus r2 square plus r1 r2 where this h is the vertical height of the frustum r1 r2 are the radii of two bases of the frustum where we take r1 to be greater than r2. Let's consider this frustum where the vertical height of the frustum that is h is given to be 9 cm. The radii r1 r2 are given to be 28 cm and 14 cm. Now the volume of the frustum of cone is given by 1 upon 3 pi h multiplied by r1 square plus r2 square plus r1 r2 and this comes out to be equal to 12,936 cm cube. Thus we have got the volume of frustum of a cone when we are given the vertical height of the cone and the radii of two bases of the frustum. Next formula that we shall discuss is for the curved surface area of a frustum of a cone. This is given by pi l multiplied by r1 plus r2 where l is the slant height of the frustum of the cone which is given by square root of h square plus r1 minus r2 the whole square and h is the vertical height of the frustum of the cone r1 r2 are the radii of the bases of the frustum of the cone. Let's consider the same example when the vertical height h of the frustum of the cone is given as 9 cm and the radii of the bases of the frustum of the cone are 28 cm and 14 cm. Now the slant height l is given by square root of h square plus r1 minus r2 the whole square which comes out to be equal to 16.64 cm. That is length of this portion is given by l equal to 16.64 cm. So now the curved surface area of frustum is equal to pi l multiplied by r1 plus r2 which is equal to 2196.48 cm square. Thus we have got the curved surface area of the frustum of the cone when we are given the vertical height of the frustum and the radii of the bases of the frustum. Next formula that we are going to discuss is for the total surface area of frustum of a cone which is given as pi l r1 plus r2 plus pi r1 square plus r2 square. Where l is the slant height of the frustum r1 r2 are the radii of the two bases of the frustum. Considering the same example where the vertical height h is given as 9 cm the radii of the bases of the frustum are given as 28 cm and 14 cm and the slant height that we have found out is equal to 16.64 cm. Thus the total surface area of the frustum is equal to pi l r1 plus r2 plus pi r1 square plus r2 square. This is equal to 2196.48 plus 3080 and this is equal to 5276.48 cm square. Thus we have got the total surface area of the frustum when we are given the vertical height h and the radii of the two bases of the frustum. This completes the session. Hope you have understood the frustum of a cone and how do we find the volume curves of this area and total surface area of the frustum of the cone.