 Hello and welcome to the session. The question says a metal pipe is 77 centimeters long. The inner diameter of the cross section is 4 centimeters. The outer diameter being 4.4 centimeters. See the figure 13.11. We have to find its inner curved surface area, an outer curved surface area and the total surface area. So let's start with the solution. And here we are given the length of the metal pipe is equal to 77 centimeters. Let us denote it by H. Also we are given the outer diameter is equal to 4.4 centimeters and the inner diameter of the pipe is equal to 4 centimeters. So first let us draw the pipe having inner diameter 4 and outer diameter 4.4 centimeters and length of the pipe as 77 centimeters. So suppose this is the rough figure of the pipe. Here its length is given to us as 77 centimeters and its inner diameter is 4 centimeters. This one and its outer diameter is 4.4 centimeters. So this implies that outer radius let us denote it by capital R is equal to outer diameter divided by 2 that is 4.4 divided by 2 and this is equal to 2.2 centimeters and inner radius denoting it by small r is equal to 4 upon 2 that is 2 centimeters. Now first let us find the inner curved surface area. Now since the pipe is of the shape of a cylinder therefore we shall be using the curved surface area of a cylinder to calculate the inner curved surface area of the pipe and the curved surface area of a cylinder is 2 pi rH where r is the radius and H is the height of the cylinder. Therefore here we have 2 pi r into H and here r is the inner radius since we are calculating the inner curved surface area. Now substituting the values of rH and pi we have 2 into 22 upon 7 into r is 2 centimeters into height that is here in this case we have length of the cylinder or the inner pipe that is 77 centimeters or 7 into 11 is 77. Therefore the inner curved surface area is equal to 968 centimeters square. Now let us find the outer curved surface area and this is equal to 2 pi r again substituting the values of pi rH into 22 upon 7 into the outer radius is 2 centimeters into H that is the length of the pipe is 77 centimeters. So this is further equal centimeters square. Here we have used the inner radius and to calculate the outer curved surface area we have used the outer radius. Now in the third part we have to find the area of the pipe which is equal to curved surface area and there is 968 centimeters square plus the outer curved surface area is 1064.8 centimeters square. So now we have to find the area of each end to calculate the total surface area of the pipe. Now this is one end and this is the other end. Now to calculate the area of these two ends we have to use the formula to calculate the area of concentric ring that is area of one end is equal to minus the area of inner pi capital r square minus pi small r square or pi into r square minus small r square and there is the area of two pi into r square minus r square capital r square minus small r square. Now substituting the values of pi capital r and small r we have 2 into 22 upon 7 into 2.2 square minus 2 square and this gives centimeters square and thus the total surface area is equal to 968 centimeters square plus 1064.8 centimeters square plus centimeters square and this is further equal to 8.08 centimeters square. Hence our answer is the inner curved surface area is 968 centimeters square its outer curved surface area is 1064.8 centimeters square and its total surface area is equal to 2038.08 centimeters square. So this completes the session. Bye and take care.