Question

how much metal sheet is required to make an open cylindrical tank of radius 4.2 M and height 1
5 m

Answer 1

radius is 4.2 meter

here

circumference = length of the metal sheet

height = breadth of the metal sheet

circumference =2*22/7*4.2(4.2 is radius)

                     length    =26.4m

                     breadth = 15 m

hence we need a metal sheet of dimensions 12.4m in length and 15 m in breadth  

                         

Answer 2

curved surface of a cylinder = 2πrh = 2×(22/7)×4.2×15 = 395.84 cm^2
area of the bottom of tank = πr^2 = (22/7)×(4.2)^2 = 55.4 cm^2
Total metal sheet required to make the tank = 395.84 + 55.4 = 451.25 cm^2