 Hi and welcome to the session. I'm Kanika and I'm going to help you to solve the following question. The question says, find the total surface area of a cone if its land height is 21 meters and diameter of its base is 24 meters. Before solving this question, we should know that what is meant by a right circular cone. The solid generated by the rotation of a right angle triangle about one of the sides containing the right angle is called a right circular cone. So if we have right angle A O B and if we rotate this right triangle about O A then we'll generate a cone like this. Point A is called the vertex of the cone. The base of this cone is circular. O B is the base radius. O A is the height of this cone and AB is its land height. We usually denote height by edge, land height by L and base radius by R. Now we should know the formula for finding the total surface area of a cone. The total surface area of a cone is equal to curve surface area of the cone that is pi R L plus area of circular base that is pi R square. The knowledge of this formula is the key idea in this question. Now begin with the solution. In the question we are given that land height that is L of the cone is equal to 21 meters and its time meter is equal to 24 meters. Now as time meter is equal to 24 meters therefore radius that is R is equal to 24 by 2 meters and this is equal to 12 meters. We know the value of R and L so we can now easily find total surface area of a cone is equal to curve surface area of a cone that is pi R L area of the circular base that is pi R square. Now substitute the value of pi R and L in this pi is equal to 22 by 7 R is equal to 12 meters L is equal to 21 meters plus again pi is equal to 22 by 7 R square is equal to square of 12 meters square and this is equal to on cancelling 21 by 7 we get 22 into 12 into 3 is equal to 792 plus 22 into 144 is 3168 upon 7 meters square and this is equal to 5,544 plus 3168 upon 7 meters square and this is equal to 8,712 upon 7 meters square and this is equal to 1244.57 meters square and the required total surface area is 1244.57 meters square this is our required answer so this completes the session by today here