 Hello and welcome to the session. In this session we will learn about pyramids. Now you must have heard or seen the Egyptian pyramids one of the seven wonders of the world. How does it appear? It has a rectangular base and the little faces are the triangle and these little faces are joined at a single point which is called apex. So we can write a pyramid is a pyramid that has one base and the little faces are triangles that are joined at a single point called the apex. Now let us discuss the types of pyramids. Now triangular pyramid, rectangular pyramid, pentagonal pyramid and so on are some types of pyramids. That is if base is a triangle then that pyramid is called a triangle pyramid and if base is a rectangle then that pyramid is called and if base is a pentagon then that pyramid is called a pyramid. If the base is a square then we have a square pyramid, if the base is a hexagon then we have a hexagonal pyramid and so on. Also in a pyramid the number of little faces that is the number of triangles depends on the number of edges of the base. Now in a triangle pyramid you can see that the number of edges of the base which is the triangle is three. So in a triangle pyramid the number of little faces in a rectangular pyramid the number of little faces is four. Then in a pentagonal pyramid the number of little faces is five. Now let us draw a pyramid. Now suppose we want to draw a triangular pyramid. In the first step we will draw a triangle as the base and the triangle as the apex. So we have drawn a triangle as the base and we have taken a point outside the triangle as the apex vertices by the apex. So we have connected the vertices of the triangle by the apex and we get as the little faces and the hidden lines must be dashed lines. In the same way we can draw the other types of pyramids also. Now to find the surface area of a pyramid. Now we know that the parts of the pyramid are base, little faces and the vertex that is apex as here you can see. In this triangle pyramid the base is the triangle BDC and triangle ABD, triangle ACD, ABC are the little faces of this triangle pyramid and A is the vertex that is the apex. Now to find the surface area we must know the altitudes of each of the little faces and the slant height of the pyramid. We can find the surface area of a pyramid by net and for this our first step is to draw the net of the pyramid. Example, and that is you have the length made of crystal in the shape of a square pyramid with slant height 8 cm and square base width side 5 cm is required to cover the length. Now here we have to find how much placed paper is required for this we have to find the surface area of the lamp so that we can find how much placed paper is required to cover the lamp. Now here this lamp is given to us which is in the shape of square pyramid. Now we have drawn a net in which first of all we have drawn a square base then at each edge we have drawn the little faces in this manner. Now surface area of the pyramid will be the sum of the areas of all the faces that is area of the base that is the triangle. Now area of the square base will be equal to side into side which is equal to 5 cm into 5 cm which is equal to 25 cm square. Now we will find the area of the triangles by the formula half into base into height so the area each triangle is equal to half into base which is 5 cm into height which is 8 cm. Now 2 into 4 is 8 to 4 is 20 so this is equal to 20 cm square. Now here the number of naked faces that is the number of triangles is 1, 2, 3 and 4. Now we have one triangle that is 20 into 4 which is equal to 8 cm square. Now the surface area of the pyramid is equal to area of the base plus areas of the little faces so the surface area of the pyramid will be equal to area of the square base which is equal to 25 cm square the little faces which is equal to 80 cm square so this is equal to 80 cm square plus 80 cm square which is equal to 105 cm square. Hence 105 cm square of base people is required to cover the length. In this manner we can find the surface area of any type of pyramid if you know the dimensions of the base and the front height. And the surface area, area of the base, areas and little faces learnt about area of pyramids. And this completes our session. Hope you all have enjoyed the session.