Question

The volume of a metallic cylindrical pipe is $748$ $c{m}^3$ its length is $14$ cm and its external radius is $9$ cm. Find its thickness.

• A. $1.5$ cm
• B. $0.5$ cm
• C. $2$ cm
• D. $1$ cm

Answer 1

The correct option is D $1$ cm

Volume of metallic rod$=\pi (R^2-r^2)\times h$

$\Rightarrow \frac{22}{7}(9^2-r^2)\times 14=748c{m}^3\Rightarrow 81-r^2=\frac{748\times 7}{22\times 14}=17$

$\Rightarrow r^2=81-17=64\Rightarrow r=\sqrt{64}=8cm$

$\therefore$Thickness $=R-r=9-8=1cm$