Question

A hemi-spherical bowl (as shown) has external radius R and internal radius r, the outer surface area of the bowl is ______.

Options

• 2πR² + πr²

• 3πR² − πr²

• 2πR² + 2πr²

• 2πR² − πr²

Answer 1

A hemi-spherical bowl (as shown) has external radius R and internal radius r, the outer surface area of the bowl is 3πR² − πr².

Explanation:

Outer surface area of the hemi-spherical bowl = Surface area of outer hemisphere + Area of outer cross-section - Area of inner cross-section

= 2πR² + πR² − πr²

= 3πR² − πr²