Question

find the volume of the iron used to make hollow cylinder of height 9cm and whose internal and external radius are 21cm and 28cm respectively ​

Answer 1

$\bold\red{\underline{\underline{Answer:}}}$

$\bold\green{\underline{\underline{Solution}}}$

$\bold{For \ hollow \ cylinder,}$

$\bold{Height=9cm}$

$\bold{Internal \ radius=21cm}$

$\bold{Externa \ radius=28cm}$

$volume \: of \: cylinder = \pi \times {r}^{2} \times h \:$

$\bold{Volume \ of \ cylinder \ with \ hollow \ part}$

$\bold{=\frac{22}{7}×28^2×9}$

$\bold{=22×4×28×9}$

$\bold{=71456cm^3}$

$\bold{Volume \ of \ hollow \ part}$

$\bold{=\frac{22}{7}×21^2×9}$

$\bold{=22×3×21×9}$

$\bold{=12474cm^3}$

$\bold{Volume \ of \ iron \ used=}$

$\bold{Volume \ of \ cylinder \ with \ hollow \ part}$

$\bold{- Volume \ of \ hollow \ part}$

${=71456-12474}$

${=58982cm^3}$

$\bold\red{Volume \ of \ iron \ used \ is \ 58982cm^3}$

Answer 2

Answer:

9702

Step-by-step explanation:

Volume of iron used= πR2h-πr2h

= π(R2-r2)h

=22/7(784-441)9

=22/7*343*9

=9702cm3