Question

The volume Of a hemisphere is 4851/2 cm 2 .find its csa

Answer 1

we knw vol of hemisphere = 2/3×22/7×r^3
4851/2×3/2×7/22=r^3
21/2=r
now
csa of hemisphere= 2×22/7×r^2
=2×22/7×21/2×21/2=693

Answer 2

The curved surface area(CSA) of a hemisphere $=693cm^2$.

Step-by-step explanation:

Given,

The volume of hemisphere = $\dfrac{4851}{2} cm^{2}$

To find, the curved surface area(CSA) of a hemisphere = ?

We know that,

The volume of a hemisphere $=\dfrac{2}{3} \pi r^{3}$

⇒$\dfrac{2}{3} \times \dfrac{22}{7} r^{3}=\dfrac{4851}{2} cm^{2}$

⇒ $r^3=(4851\times 7 \times 3)/(2 \times 2 \times 22)$

⇒ $r^3=\dfrac{101871}{88}$

⇒ $r^3 = 1157.625$

⇒ $r^3 = \dfrac{1157625}{100}$

⇒ $r^3 = (\dfrac{105}{10})^{3} =10.5^{2}$

⇒ r = 10.5 cm

∴ The curved surface area(CSA) of a hemisphere $=2\pi r^{2}$

$= 2 \times \dfrac{22}{7}  \times 10.5 \times 10.5$

$= 2 \times 22  \times 1.5 \times 10.5cm^{2}$

$= 44  \times 15.75cm^{2}$

$=693cm^2$

Hence, the curved surface area(CSA) of a hemisphere $=693cm^2$.