A closed cylindrical tank of radius 7 cm and height 5 m is made from a sheet of metal. If the breadth of the rectangular sheet is 10 m, then find the length of the sheet.

Solution

Here, Radius (r) = 7 cm
Height (h) = 5 cm
Since, total surface area of the closed cylinder
$space space equals 2 πr left parenthesis straight r plus straight h right parenthesis$
∴ Total surface area of the cylinder tank
$equals space 2 cross times 22 over 7 cross times left parenthesis 7 right parenthesis cross times left parenthesis 7 plus 5 right parenthesis space straight m squared$
$equals space 2 cross times 22 cross times 12 space straight m squared$
$equals space 528 space straight m squared$
Let, the length of the sheet required = 'l' m
∴ Area of the rectangular sheet = l x 10 m²
$rightwards double arrow$ l x 10 = 528
$rightwards double arrow$ $straight l equals 528 over 10 space straight m$