Question

the curved surface area of a hollow cylinder is 5220 it is cut along it's height and formed into a rectangular sheet of width 36cm find the perimeter of the rectangular sheet

Answer 1

$curved \: surface \: area \: = 5220cm {}^{2}$

if we imagine a hollow cylinder ,

the boundary of the top is circumference which
$2\pi \: r$
when it is cut along height this circumference will become the length

and

the height will become the width


$2\pi \: rh \: = 2\pi \: r \times h$
let the height be h


$5220 = 2\pi \: r \: \times 36$

$\frac{5220}{36} = 2\pi \: r$
= 145

so, length os 145 cm

Perimeter = 2 ( l + b )

= 2 ( 145 + 36) cm

= 362 cm

the perimeter is 362cm