A closed cylindrical tank of radius 7 m and height 3 m is made from a sheet of metal. How much sheet of metal is required?

Solution

Here, r = 7 m and h = 3 m
∴ Total surface area = $2 πr left parenthesis straight r plus straight h right parenthesis$
= $2 cross times 22 over 7 cross times 7 cross times left parenthesis 7 plus 3 right parenthesis space straight m squared$
= $2 cross times 22 over 7 cross times 7 cross times 10 space straight m squared$
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$space space equals space 440 space straight m squared$
Thus, $440 space straight m squared$ metal is required.