Question

What is the volume of the aluminium used to make a hemisphere of inner radius 7 cm and thickness 1 cm?
[$use\pi =\frac{22}{7}$]

• A. $353.773c{m}^3$
• B. $228.67c{m}^3$
• C. $257.14c{m}^3$
• D. $341.34c{m}^3$

Answer 1

The correct option is A $353.773c{m}^3$

Given,
Inner radius
$=7cm$

Outer radius
$=7cm+thickness$
$=7cm+1cm$
$=8cm$

We know that,
Volume of hemisphere
$=\frac{2}{3}\pi r^3$

Volume with inner radius
$=\frac{2}{3}\pi \times 7^3$
$=718.013c{m}^3$

Volume with outer radius
$=\frac{2}{3}\pi \times 8^3$
$=1071.78c{m}^2$

$\therefore$ Volume of aluminum used
= Volume with outer radius - Volume with inner radius
$=1071.78-718.013$
$=353.773c{m}^3$