Question

Find the curved
surface area and
(ii) the total surfacehemisphere
radius 21cm​

Answer 1

Given :-

• radius of the hemisphere= 21 cm

To Find :-

• curved surface area and total surface area of the hemisphere ?

Solution :-

we know that,

$\boxed{ \bold{C.S.A \: of \: hemisphere = 2\pi {r}^{2} }}$

$\bold{: \implies 2 \times \frac{22}{ \cancel7} \times \cancel{ 21} \times 21 } \\ \\ \bold{ : \implies 2 \times 22 \times 3 \times 21} \: \: \: \: \\ \\ \bold{: \implies 2772 \: {cm }^{2} } \: \: \: \: \: \: \: \: \: \: \: \: \: \: \:$

so, Curved surface area of the hemisphere is 2772 cm²

__________________________

and now, we know that,

$\boxed{ \bold{T.S.A \: of \: hemisphere = 3\pi {r}^{2} }}$

$\bold{: \implies 3 \times \frac{22}{ \cancel7} \times \cancel{ 21} \times 21 } \\ \\ \bold{: \implies 3 \times 22 \times 3 \times 21 } \: \: \: \: \\ \\ \bold{: \implies 4158 \: {cm}^{2} } \: \: \: \: \: \: \: \: \: \: \: \: \: \: \:$

so, total surface area of the hemisphere is 4158 cm²