Question

The total surface area of an open pipe of length H cm, external radius R cm and internal radius r cm, is ______.

विकल्प

• πR² − πr² + 2π(R − r) H

• 2πR² − 2πr² + 2πRH

• 2πRH − 2πrh + πR² − πr²

• 2(πR² − πr²) + 2πRH + 2πrH

Answer 1

The total surface area of an open pipe of length H cm, external radius R cm and internal radius r cm, is 2(πR² − πr²) + 2πRH + 2πrH.

Explanation:

Given,

External radius = R cm,

Internal radius = r cm,

Height = H cm.

Total surface area of hollow cylinder = External curved surface area + Internal curved surface area + 2(Area of cross section)

= 2πRH + 2πrH + 2(πR² − πr²)