Question

A solid cylinder of radius r and height h is placed over other cylinder of same height and radius. The total surface area of the shape so formed is ______.

Options

• 4πrh + 4πr²

• 4πrh - 4πr²

• 4πrh + 2πr²

• 4πrh - 2πr²

Answer 1

A solid cylinder of radius r and height h is placed over other cylinder of same height and radius. The total surface area of the shape so formed is 4πrh + 2πr².

Explanation:

Since the total surface area of cylinder of radius r and height h = 2πrh + 2πr².

When one cylinder is placed over the other cylinder of same height and radius,

Then height of new cylinder = 2h

And radius of the new cylinder = r

Therefore total surface area of new cylinder

= 2πr (2h) + 2πr²

= 4πrh + 2πr²