Question

An open hollow cylindrical container, made of very thin metal sheet, has radius r cm and height h cm, its total surface area (in cm²) is ______.

विकल्प

• πr²h + 2πrh

• 4πrh + πr²

• 4πrh + 2πr²

• 2πrh + 2πr²

Answer 1

An open hollow cylindrical container, made of very thin metal sheet, has radius r cm and height h cm, its total surface area (in \(\mathrm{cm}^{2}\) ) is 4πrh + πr².

Explanation:

Given,

It is an open hollow cylindrical container.

∴ It will be open at one end and closed at the other end.

Since, hollow cylindrical container is made up of very thin metal sheet.

∴ External radius = Internal radius = r cm.

Given,

Height = h cm.

Total surface area of hollow cylinder = External curved surface area + Internal curved surface area + Area of cross section (lower end)

= 2πrh + 2πrh + πr²

= 4πrh + πr²