Curved Surface Area Solution4





In this page curved surface area solution4 we are going to see solution of some practice questions.

Question 8

The external surface area of a hollow cylinder is 540 Π cm².Its internal diameter is 16 cm and height is 15 cm. Find the total surface area.

Solution:

External surface area of cylinder = 540 Π cm²

                                 2 Π R h = 540 Π cm²

Internal radius (r) = 16/2 = 8 cm

       height (h) = 15 cm

  2 x Π x R x h = 540 Π 

  2 x Π x R x 15 = 540 Π

                     = 540 Π x (1/2) x (1/Π) x (1/15)

                    = 270/(15)

                 R= 18

Total surface area =  2 Π (R + r) (R - r + h)

                                 =  2 Π (18 + 8) (18 - 8 + 15)

                                 =  2 Π (26) (25)

                                 =  1300 Π cm²

Total surface area of the cylinder = 1300 Π cm²


Question 9

The external diameter of the cylindrical shaped iron pipe is 25 cm and its length is 20 cm. If the thickness of the pipe is 1 cm, find the total surface area of the pipe.

Solution:

External radius of the pipe (R) = 12.5 cm

height of the pipe (h) = 20 cm

thickness of the pipe (w) = 1 cm

To find total surface area of the cylinder we have to find the internal radius (r)

      W = R - r

       1 = 12.5 - r

       r = 12.5 - 1

      r = 11 .5 cm

Total surface area = 2 Π (R + r) (R - r + h)

                          = 2 Π (12.5 + 11.5) (12.5 - 11.5 + 20)

                          = 2 (22/7) (24) (21)

                          = 2 (22) (24) (3)

                          = 3168 cm²

curved surface area solution4 curved surface area solution4