Question

A hemispherical bowl is made of brass, 7 cm thickness. The inner radius of the bowl is 7 cm. Find the ratio of outer surface area to inner surface area.

• A. $4:1$
  
• B. $1:4$
  
• C. $2:1$
• D. $1:2$

Answer 1

The correct option is A $4:1$


We know that,
curved surface area of hemsiphere
$=2\pi r^2$

Now,

Curved surface area for inner surface
$=2\pi \times 7^2$
$=98\pi c{m}^2$

Curved surface area for outer surface
$=2\pi \times {14}^2$
$=392\pi c{m}^2$

So,
$=\frac{Curvedsurfaceareaforoutersurface}{Curvedsurfaceareaforinnersurface}$

$=\frac{392\pi c{m}^2}{98\pi c{m}^2}$

$=\frac{4}{1}$

$=4:1$